Wavelength combiner photonic integrated circuit with grating coupling of lasers

ABSTRACT

Systems, devices, and methods of manufacturing optical engines and laser projectors that are well-suited for use in wearable heads-up displays (WHUDs) are described. Generally, the optical engines of the present disclosure integrate a plurality of laser diodes (e.g., 3 laser diodes, 4 laser diodes) within a single, hermetically or partially hermetically sealed, encapsulated package. Photonic integrated circuits having grating couplers thereon may be used to wavelength multiplex beams of light emitted by the plurality of laser diodes into a coaxially superimposed aggregate beam. Such optical engines may have various advantages over existing designs including, for example, smaller volumes, better manufacturability, faster modulation speed, etc. WHUDs that employ such optical engines and laser projectors are also described.

BACKGROUND Technical Field

The present disclosure is generally directed to systems, devices, andmethods relating to optical engines, for example, optical engines forlaser projectors used in wearable heads-up displays or otherapplications.

Description of the Related Art

A projector is an optical device that projects or shines a pattern oflight onto another object (e.g., onto a surface of another object, suchas onto a projection screen) in order to display an image or video onthat other object. A projector necessarily includes a light source, anda laser projector is a projector for which the light source comprises atleast one laser. The at least one laser is temporally modulated toprovide a pattern of laser light and usually at least one controllablemirror is used to spatially distribute the modulated pattern of laserlight over a two-dimensional area of another object. The spatialdistribution of the modulated pattern of laser light produces an imageat or on the other object. In conventional scanning laser projectors, atleast one controllable mirror may be used to control the spatialdistribution, and may include: a single digital micromirror (e.g., amicroelectromechanical system (“MEMS”) based digital micromirror) thatis controllably rotatable or deformable in two dimensions, or twodigital micromirrors that are each controllably rotatable or deformableabout a respective dimension, or a digital light processing (“DLP”) chipcomprising an array of digital micromirrors.

In a conventional laser projector comprising an RGB (red/green/blue)laser module with a red laser diode, a green laser diode, and a bluelaser diode, each respective laser diode may have a correspondingrespective focusing lens. Each of the laser diodes of a laser module aretypically housed in a separate package (e.g., a TO-38 package or “can”).The relative positions of the laser diodes, the focusing lenses, and theat least one controllable mirror are all tuned and aligned so that eachlaser beam impinges on the at least one controllable mirror withsubstantially the same spot size and with substantially the same rate ofconvergence (so that all laser beams will continue to have substantiallythe same spot size as they propagate away from the laser projectortowards, e.g., a projection screen). In a conventional laser projector,it is usually possible to come up with such a configuration for allthese elements because the overall form factor of the device is not aprimary design consideration. However, in applications for which theform factor of the laser projector is an important design element, itcan be very challenging to find a configuration for the laser diodes,the focusing lenses, and the at least one controllable mirror thatsufficiently aligns the laser beams (at least in terms of spot size,spot position, and rate of convergence) while satisfying the form factorconstraints.

A head-mounted display is an electronic device that is worn on a user'shead and, when so worn, secures at least one electronic display within aviewable field of at least one of the user's eyes, regardless of theposition or orientation of the user's head. A wearable heads-up displayis a head-mounted display that enables the user to see displayed contentbut also does not prevent the user from being able to see their externalenvironment. The “display” component of a wearable heads-up display iseither transparent or at a periphery of the user's field of view so thatit does not completely block the user from being able to see theirexternal environment. A “combiner” component of a wearable heads-updisplay is the physical structure where display light and environmentallight merge as one within the user's field of view. The combiner of awearable heads-up display is typically transparent to environmentallight but includes some optical routing mechanism to direct displaylight into the user's field of view.

Examples of wearable heads-up displays include: the Google Glass®, theOptinvent Ora®, the Epson Moverio®, and the Sony Glasstron®, just toname a few.

The optical performance of a wearable heads-up display is an importantfactor in its design. When it comes to face-worn devices, users alsocare a lot about aesthetics and comfort. This is clearly highlighted bythe immensity of the eyeglass (including sunglass) frame industry.Independent of their performance limitations, many of the aforementionedexamples of wearable heads-up displays have struggled to find tractionin consumer markets because, at least in part, they lack fashion appealor comfort. Most wearable heads-up displays presented to date employrelatively large components and, as a result, are considerably bulkier,less comfortable and less stylish than conventional eyeglass frames.

Direct Laser Writing

Femtosecond laser micro-machining is a direct-laser-write and rapidprototyping technique that provides great potential for optical devicefabrication. Strong focusing of femtosecond laser light into transparentglass can induce positive refractive index modifications up to 0.01refractive index units (RIU) within the material and without surfacedamage. Since then, ultrafast (femto/pico-second) lasers have been shownto enable flexible 3D structuring of various glasses, and has led to thedemonstration of many types of optical devices (waveguides, couplers,Bragg gratings, waveplates, etc.) that serve as building blocks for 3Doptical circuits.

Direct-laser-writing uses ultrashort laser pulses to confine strongnonlinear optical interactions that may induce, for example, positive ornegative refractive index changes in bulk transparent materials forcreating optical waveguides (WGs). The mechanisms by whichdirect-laser-write modifications occur include, but are not limited to,multiphoton ionization, avalanche ionization, electron-atom collisions,plasma interactions, thermal effects (e.g. diffusion, heataccumulation), energy dissipation, and material cooling leading toinhomogeneous solidification. For direct-laser-writing waveguides,waveguide performance can be tuned and optimized by, but not limited to,the writing laser's properties (pulse duration, pulse temporal shape,bandwidth and shape, pulse repetition rate, wavelength, polarization,and beam spatial shape) and the focusing conditions (lens numericalaperture, air/liquid immersion, translation direction and speeds).

BRIEF SUMMARY

An optical engine may be summarized as including a base substrate; aplurality of laser diodes, each of the plurality of laser diodes bondeddirectly or indirectly to the base substrate; at least one laser diodedriver circuit operatively coupled to the plurality of laser diodes toselectively drive current to the plurality of laser diodes; a capcomprising at least one wall and at least one optical window that,together with the base substrate, define an interior volume sized anddimensioned to receive at least the plurality of laser diodes, the capbeing bonded to the base substrate to provide a hermetic or partiallyhermetic seal between the interior volume of the cap and a volumeexterior to the cap, and the optical window positioned and oriented toallow beams of light emitted from the plurality of laser diodes to exitthe interior volume; and a photonic integrated circuit comprising aplurality of input facets and at least one output facet, in operation,the photonic integrated circuit receives a plurality of beams of lightat the respective plurality of input facets and wavelength multiplexesthe plurality of beams of light to provide an aggregated beam of lightat the output facet.

The optical engine may further include a plurality of collimationlenses, each of the plurality of collimation lenses positioned andoriented to collimate light received from respective ones of the beamsof light emitted from the plurality of laser diodes, and to output thecollimated light toward to the plurality of input facets of the photonicintegrated circuit. Each of the plurality of collimation lenses may bepositioned within the interior volume. Each of the plurality ofcollimation lenses may be bonded to the optical window of the cap. Thephotonic integrated circuit may be bonded to the optical window of thecap.

The optical engine may further include an optical director elementdisposed within the interior volume, the optical director element bondedto the base substrate proximate the plurality of laser diodes, andpositioned and oriented to reflect laser light from the plurality oflaser diodes toward the optical window of the cap. The optical directorelement may include a mirror or a prism.

The optical engine may further include a collimation lens positioned andoriented to receive and collimate the aggregate beam of light from theoutput facet of the photonic integrated circuit. The collimation lensmay include an achromatic lens. The collimation lens may include anapochromatic lens.

The optical engine may further include at least one diffractive opticalelement positioned and oriented to receive the aggregate beam of light,in operation, the at least one diffractive optical element provideswavelength dependent focus correction for the aggregate beam of light.

The optical engine may further include a plurality of chip submountsbonded to the base substrate, wherein each of the laser diodes arebonded to a corresponding one of the plurality of chip submounts. Theplurality of laser diodes may include a red laser diode to provide a redlaser light, a green laser diode to provide a green laser light, a bluelaser diode to provide a blue laser light, and an infrared laser diodeto provide infrared laser light. The base substrate may be formed fromat least one of low temperature co-fired ceramic (LTCC), aluminumnitride (AlN), alumina, or Kovar®. The at least one laser diode drivercircuit may be bonded to a first surface of the base substrate, and theplurality of laser diodes and the cap may be bonded to a second surfaceof the base substrate, the second surface of the base substrate oppositethe first surface of the base substrate. The at least one laser diodedriver circuit, the plurality of laser diodes, and the cap may be bondedto a first surface of the base substrate. The plurality of laser diodesand the cap may be bonded to the base substrate, and the at least onelaser diode driver circuit may be bonded to another substrate separatefrom the base substrate. Each of the laser diodes may include one of anedge emitter laser or a vertical-cavity surface-emitting laser (VCSEL).The at least one wall of the cap may include at least one continuoussidewall having a lower first end and an upper second end, the lowerfirst end bonded to the base substrate, and the optical window may behermetically or partially hermetically sealed to the cap proximate theupper second end.

The photonic integrated circuit may include a plurality of waveguides,each waveguide of the plurality of waveguides to receive laser lightfrom a respective laser diode of the plurality of laser diodes. Eachwaveguide of the plurality of waveguides may be optimized to receive andoutput laser light having a wavelength corresponding to the wavelengthof laser light received from the respective laser diode. The pluralityof waveguides may include a waveguide combiner. The waveguide combinermay include at least one of: a directional coupler, Y-branch, whisperinggallery mode, or multi-mode interface coupler. Each waveguide of theplurality of waveguides may include an input facet to receive laserlight from a respective laser diode of the plurality of laser diodes andan output facet to output the received laser light, a spacing betweenthe output facets of each waveguide being smaller than a spacing betweenthe input facets of each waveguide.

Each input facet of the plurality of input facets may be a grating inputcoupler. Each input facet of the plurality of input facets may be aplanar region with an index of refraction lower than an index ofrefraction of material from which the photonic integrated circuit isformed.

A wearable heads-up display (WHUD) may be summarized as including asupport structure that in use is worn on the head of a user; a laserprojector carried by the support structure, the laser projectorincluding an optical engine, including a base substrate; a plurality oflaser diodes, each of the plurality of laser diodes bonded directly orindirectly to the base substrate; at least one laser diode drivercircuit operatively coupled to the plurality of laser diodes toselectively drive current to the plurality of laser diodes; a capcomprising at least one wall and at least one optical window that,together with the base substrate, define an interior volume sized anddimensioned to receive at least the plurality of laser diodes, the capbeing bonded to the base substrate to provide a hermetic or partiallyhermetic seal between the interior volume of the cap and a volumeexterior to the cap, and the optical window positioned and oriented toallow beams of light emitted from the plurality of laser diodes to exitthe interior volume; and a photonic integrated circuit comprising aplurality of input facets and at least one output facet, in operation,the photonic integrated circuit receives a plurality of beams of lightat the respective plurality of input facets and wavelength multiplexesthe plurality of beams of light to provide an aggregated beam of lightat the output facet; and at least one scan mirror positioned to receivethe aggregate beam of light output at the output facet of the photonicintegrated circuit, the at least one scan mirror controllably orientableto redirect the aggregate beam of light over a range of angles.

The WHUD may further include a processor communicatively coupled to thelaser projector to modulate the generation of light signals.

The WHUD may further include a transparent combiner carried by thesupport structure and positioned within a field of view of the user, inoperation the transparent combiner directs laser light from an output ofthe laser projector into the field of view of the user.

The optical engine of the WHUD may further include a collimation lenspositioned and oriented to receive and collimate the aggregate beam oflight from the output coupler of the photonic integrated circuit. Thecollimation lens may include an achromatic lens or an apochromatic lens.

The optical engine of the WHUD further may include at least onediffractive optical element positioned and oriented to receive theaggregate beam of light, in operation, the at least one diffractiveoptical element provides wavelength dependent focus correction for theaggregate beam of light.

The optical engine of the WHUD may further include a plurality ofcollimation lenses, each of the plurality of collimation lensespositioned and oriented to collimate light received from respective onesof the beams of light emitted from the plurality of laser diodes, and tooutput the collimated light toward to the plurality of input facets ofthe photonic integrated circuit. The photonic integrated circuit may bebonded to the optical window of the cap.

The optical engine of the WHUD may further include an optical directorelement disposed within the interior volume, the optical directorelement bonded to the base substrate proximate the plurality of laserdiodes, and positioned and oriented to reflect laser light from theplurality of laser diodes toward the optical window of the cap. Theoptical engine of the WHUD may further include a plurality of chipsubmounts bonded to the base substrate, wherein each of the laser diodesare bonded to a corresponding one of the plurality of chip submounts.The plurality of laser diodes may include a red laser diode to provide ared laser light, a green laser diode to provide a green laser light, ablue laser diode to provide a blue laser light, and an infrared laserdiode to provide infrared laser light.

The at least one laser diode driver circuit may be bonded to a firstsurface of the base substrate, and the plurality of laser diodes and thecap may be bonded to a second surface of the base substrate, the secondsurface of the base substrate opposite the first surface of the basesubstrate. The at least one laser diode driver circuit, the plurality oflaser diodes, and the cap may be bonded to a first surface of the basesubstrate. The plurality of laser diodes and the cap may be bonded to afirst surface of the base substrate, and the at least one laser diodedriver circuit may be mounted to the support structure.

Each of the laser diodes may include one of an edge emitter laser or avertical-cavity surface-emitting laser (VCSEL). The at least one wall ofthe cap may include at least one continuous sidewall having a lowerfirst end and an upper second end, the lower first end bonded to thebase substrate, and the optical window may be hermetically or partiallyhermetically sealed to the cap proximate the upper second end.

The photonic integrated circuit may include a plurality of waveguides,each waveguide of the plurality of waveguides to receive laser lightfrom a respective laser diode of the plurality of laser diodes. Eachwaveguide of the plurality of waveguides may be optimized to receive andoutput laser light having a wavelength corresponding to the wavelengthof laser light received from the respective laser diode. The pluralityof waveguides may include a waveguide combiner. The waveguide combinermay include at least one of: a directional coupler, Y-branch, whisperinggallery mode, or multi-mode interface coupler. Each waveguide of theplurality of waveguides may include an input facet to receive laserlight from a respective laser diode of the plurality of laser diodes andan output facet to output the received laser light, a spacing betweenthe output facets of each waveguide being smaller than a spacing betweenthe input facets of each waveguide.

Each input facet of the plurality of input facets may be a grating inputcoupler. Each input facet of the plurality of input facets may be aplanar region with an index of refraction lower than an index ofrefraction of material from which the photonic integrated circuit isformed.

A laser projector may be summarized as including an optical engine,comprising: a base substrate; a plurality of laser diodes, each of theplurality of laser diodes bonded directly or indirectly to the basesubstrate; at least one laser diode driver circuit operatively coupledto the plurality of laser diodes to selectively drive current to theplurality of laser diodes; a cap comprising at least one wall and atleast one optical window that, together with the base substrate, definean interior volume sized and dimensioned to receive at least theplurality of laser diodes, the cap being bonded to the base substrate toprovide a hermetic or partially hermetic seal between the interiorvolume of the cap and a volume exterior to the cap, and the opticalwindow positioned and oriented to allow beams of light emitted from theplurality of laser diodes to exit the interior volume; and a photonicintegrated circuit comprising a plurality of input facets and at leastone output facet, in operation, the photonic integrated circuit receivesa plurality of beams of light at the respective plurality of inputfacets and wavelength multiplexes the plurality of beams of light toprovide an aggregated beam of light at the output facet; and at leastone scan mirror positioned to receive the aggregate beam of light outputat the output facet of the photonic integrated circuit, the at least onescan mirror controllably orientable to redirect the aggregate beam oflight over a range of angles.

The laser projector may further include a processor communicativelycoupled to the optical engine to modulate the generation of lightsignals.

The optical engine of the laser projector may further include aplurality of collimation lenses, each of the plurality of collimationlenses positioned and oriented to collimate light received fromrespective ones of the beams of light emitted from the plurality oflaser diodes, and to output the collimated light toward to the pluralityof input facets of the photonic integrated circuit. Each of theplurality of collimation lenses may be bonded to the optical window ofthe cap. The photonic integrated circuit may be bonded to the opticalwindow of the cap.

The optical engine of the laser projector may further include an opticaldirector element disposed within the interior volume, the opticaldirector element bonded to the base substrate proximate the plurality oflaser diodes, and positioned and oriented to reflect laser light fromthe plurality of laser diodes toward the optical window of the cap. Theoptical engine of the laser projector may further include a collimationlens positioned and oriented to receive and collimate the aggregate beamof light from the output facet of the photonic integrated circuit. Theoptical engine of the laser projector may further include at least onediffractive optical element positioned and oriented to receive theaggregate beam of light, in operation, the at least one diffractiveoptical element provides wavelength dependent focus correction for theaggregate beam of light.

The optical engine of the laser projector may further include aplurality of chip submounts bonded to the base substrate, wherein eachof the laser diodes are bonded to a corresponding one of the pluralityof chip submounts. The plurality of laser diodes may include a red laserdiode to provide a red laser light, a green laser diode to provide agreen laser light, a blue laser diode to provide a blue laser light, andan infrared laser diode to provide infrared laser light.

The at least one laser diode driver circuit may be bonded to a firstsurface of the base substrate, and the plurality of laser diodes and thecap may be bonded to a second surface of the base substrate, the secondsurface of the base substrate opposite the first surface of the basesubstrate. The at least one laser diode driver circuit, the plurality oflaser diodes, and the cap may be bonded to a first surface of the basesubstrate. The plurality of laser diodes and the cap may be bonded tothe base substrate, and the at least one laser diode driver circuit maybe bonded to another substrate separate from the base substrate.

Each of the laser diodes may include one of an edge emitter laser or avertical-cavity surface-emitting laser (VCSEL). The at least one wall ofthe cap may include at least one continuous sidewall having a lowerfirst end and an upper second end, the lower first end bonded to thebase substrate, and the optical window may be hermetically or partiallyhermetically sealed to the cap proximate the upper second end.

The photonic integrated circuit may include a plurality of waveguides,each waveguide of the plurality of waveguides to receive laser lightfrom a respective laser diode of the plurality of laser diodes. Eachwaveguide of the plurality of waveguides may be optimized to receive andoutput laser light having a wavelength corresponding to the wavelengthof laser light received from the respective laser diode. The pluralityof waveguides may include a waveguide combiner. The waveguide combinermay include at least one of: a directional coupler, Y-branch, whisperinggallery mode, or multi-mode interface coupler. Each waveguide of theplurality of waveguides may include an input facet to receive laserlight from a respective laser diode of the plurality of laser diodes andan output facet to output the received laser light, a spacing betweenthe output facets of each waveguide being smaller than a spacing betweenthe input facets of each waveguide.

Each input facet of the plurality of input facets may be a grating inputcoupler. Each input facet of the plurality of input facets may be aplanar region with an index of refraction lower than an index ofrefraction of material from which the photonic integrated circuit isformed.

A method of operating an optical engine, the optical engine including aplurality of laser diodes hermetically or partially hermetically sealedin an encapsulated package, may be summarized as including causing theplurality of laser diodes to generate a corresponding plurality of beamsof laser light through an optical window in the encapsulated package;coupling the plurality of beams of laser light into a respectiveplurality of input facets of a photonic integrated circuit; andwavelength multiplexing, by the photonic integrated circuit, the beamsof laser light to generate an aggregate beam of light at an output facetof the photonic integrated circuit.

The method may further include collimating, by a collimation lens, theaggregate beam of light that exits from the output facet of the photonicintegrated circuit. Collimating the aggregate beam of light may includecollimating the aggregate beam of light using an achromatic lens or anapochromatic lens.

The method may further include correcting, by at least one diffractiveelement, wavelength dependent focus for the aggregate beam of light.Causing the plurality of laser diodes to generate laser light mayinclude causing a red laser diode to generate red laser light, causing agreen laser diode to generate green laser light, causing a blue laserdiode to generate blue laser light, and causing an infrared laser diodeto generate infrared laser light. Coupling the plurality of beams oflaser light into a respective plurality of input facets of a photonicintegrated circuit may include coupling the plurality of beams of laserlight into a respective plurality of input facets of a photonicintegrated circuit via a plurality of collimation lenses.

Wavelength multiplexing, by the photonic integrated circuit, the beamsof laser light may include receiving, by each waveguide of a pluralityof waveguides, laser light from a respective laser diode of theplurality of laser diodes, and outputting, by the plurality ofwaveguides, an aggregate beam of light.

The photonic integrated circuit may include a waveguide combiner whichincludes the plurality of input facets and the output facet, andwavelength multiplexing, by the photonic integrated circuit, the beamsof laser light may include: receiving, by each input facet of theplurality of input facets, laser light from a respective laser diode ofthe plurality of laser diodes; and outputting, by the output facet ofthe waveguide combiner, a coaxially superimposed aggregate beam oflight.

The photonic integrated circuit may include a plurality of waveguides,each waveguide of the plurality of waveguides including an input facetand an output facet, and wavelength multiplexing, by the photonicintegrated circuit, the beams of laser light may include: receiving, bythe respective input facet of each waveguide of the plurality ofwaveguides, laser light from a respective laser diode of the pluralityof laser diodes; and outputting, by the respective output facet of eachwaveguide of the plurality of waveguides, a beam of light, a spacingbetween the output facet of each waveguide being smaller than a spacingbetween the input facets of each waveguide to produce an aggregate beamof light.

Coupling the plurality of beams of laser light into a respectiveplurality of input facets of a photonic integrated circuit may includecoupling the plurality of beams of laser light into a respectiveplurality of grating input couplers of the photonic integrated circuit.Coupling the plurality of beams of laser light into a respectiveplurality of input facets of a photonic integrated circuit may includecoupling the plurality of beams of laser light into the photonicintegrated circuit via a plurality of planar regions with an index ofrefraction lower than an index of refraction of material from which thephotonic integrated circuit is formed.

An optical engine may be summarized as including a base substrate; aplurality of laser diodes, each of the plurality of laser diodes bondeddirectly or indirectly to the base substrate; a cap comprising at leastone wall that, with the base substrate, defines an interior volume sizedand dimensioned to receive at least the plurality of laser diodes, thecap being bonded to the base substrate to provide a hermetic orpartially hermetic seal between the interior volume of the cap and avolume exterior to the cap; and a photonic integrated circuit comprisinga plurality of input facets and at least one output facet, in operation,the photonic integrated circuit receives a plurality of beams of lightat respective ones of the plurality of input facets and wavelengthmultiplexes the plurality of beams of light to provide an aggregatedbeam of light at the output facet. Each of the plurality of laser diodesmay be positioned immediately adjacent a respective one of the pluralityof input facets of the photonic integrated circuit. Each of theplurality of input facets of the photonic integrated circuit may bepositioned inside the interior volume and the at least one output facetof the photonic integrated circuit may be positioned outside of theinterior volume. The cap may include at least one optical windowpositioned and oriented to allow beams of light emitted from theplurality of laser diodes to exit the interior volume.

The photonic integrated circuit may be bonded to the optical window ofthe cap. The at least one wall of the cap may include at least onecontinuous sidewall having a lower first end and an upper second end,the lower first end bonded to the base substrate, and the optical windowmay be hermetically or partially hermetically sealed to the capproximate the upper second end. The optical engine may further includean optical director element disposed within the interior volume, theoptical director element bonded to the base substrate proximate theplurality of laser diodes, and positioned and oriented to reflect laserlight from the plurality of laser diodes toward the optical window ofthe cap.

The optical engine may further include a plurality of collimationlenses, each of the plurality of collimation lenses positioned andoriented to collimate light received from respective ones of beams oflight emitted from the plurality of laser diodes, and to output thecollimated light toward to the plurality of input facets of the photonicintegrated circuit. The optical engine may further include a collimationlens positioned and oriented to receive and collimate the aggregate beamof light from the output facet of the photonic integrated circuit. Theoptical engine may further include at least one diffractive opticalelement positioned and oriented to receive the aggregate beam of light,in operation, the at least one diffractive optical element provideswavelength dependent focus correction for the aggregate beam of light.

The optical engine may further include a plurality of chip submountsbonded to the base substrate, wherein each of the laser diodes arebonded to a corresponding one of the plurality of chip submounts. Theplurality of laser diodes may include a red laser diode to provide a redlaser light, a green laser diode to provide a green laser light, a bluelaser diode to provide a blue laser light, and an infrared laser diodeto provide infrared laser light.

The optical engine may further include at least one laser diode drivercircuit operatively coupled to the plurality of laser diodes toselectively drive current to the plurality of laser diodes. The at leastone laser diode driver circuit may be bonded to a first surface of thebase substrate, and the plurality of laser diodes and the cap may bebonded to a second surface of the base substrate, the second surface ofthe base substrate opposite the first surface of the base substrate. Theat least one laser diode driver circuit, the plurality of laser diodes,and the cap may be bonded to a first surface of the base substrate. Theplurality of laser diodes and the cap may be bonded to the basesubstrate, and the at least one laser diode driver circuit may be bondedto another substrate separate from the base substrate. Each of the laserdiodes may include one of an edge emitter laser or a vertical-cavitysurface-emitting laser (VCSEL).

The photonic integrated circuit may include a plurality of waveguides,each waveguide of the plurality of waveguides to receive laser lightfrom a respective laser diode of the plurality of laser diodes. Eachwaveguide of the plurality of waveguides may be optimized to receive andoutput laser light having a wavelength corresponding to the wavelengthof laser light received from the respective laser diode. The pluralityof waveguides may include a waveguide combiner. The waveguide combinermay include at least one of: a directional coupler, Y-branch, whisperinggallery mode, or multi-mode interface coupler. Each waveguide of theplurality of waveguides may include an input facet to receive laserlight from a respective laser diode of the plurality of laser diodes andan output facet to output the received laser light, a spacing betweenthe output couplers of each waveguide being smaller than a spacingbetween the input facets of each waveguide.

Each input facet of the plurality of input facets may be a grating inputcoupler. Each input facet of the plurality of input facets may be aplanar region with an index of refraction lower than an index ofrefraction of material from which the photonic integrated circuit isformed.

A method of manufacturing an optical engine may be summarized asincluding: bonding a plurality of laser diodes directly or indirectly toa base substrate; bonding a cap to the base substrate, the capcomprising at least one wall that, with the base substrate, defines aninterior volume sized and dimensioned to receive at least the pluralityof laser diodes, the cap being bonded to the base substrate to provide ahermetic or partially hermetic seal between the interior volume of thecap and a volume exterior to the cap; and bonding a photonic integratedcircuit comprising a plurality of input facets and at least one outputfacet to the cap, in operation, each input facet of the photonicintegrated circuit receives a respective beam of light of a plurality ofbeams of light, and the photonic integrated circuit wavelengthmultiplexes the plurality of beams of light to provide an aggregatedbeam of light at the output facet.

The method may further include: bonding each of the laser diodesindirectly to the base substrate by bonding each laser diode to arespective chip submount; and bonding each chip submount to the basesubstrate. Bonding each laser diode to a respective chip submount mayinclude bonding each laser diode to a respective chip submount using aeutectic gold tin (AuSn) solder process. Bonding each chip submount tothe base substrate may include step-soldering each chip submount to thebase substrate. Bonding each chip submount to the base substrate mayinclude bonding each chip submount to the base substrate using at leastone of a reflow oven process, thermosonic bonding, thermocompressionbonding, transient liquid phase (TLP) bonding, or laser soldering.Bonding each chip submount to the base substrate may include bonding achip submount that has a red laser diode bonded thereto, bonding a chipsubmount that has a green laser diode bonded thereto, bonding a chipsubmount that has a blue laser diode bonded thereto, and bonding a chipsubmount that has an infrared laser diode bonded thereto.

The method may further include bonding a plurality of collimation lensesbetween the plurality of laser diodes and the plurality of input facetsof the photonic integrated circuit, each of the plurality of collimationlenses positioned and oriented to collimate light received fromrespective ones of the beams of light emitted from the plurality oflaser diodes, and to output the collimated light toward the plurality ofinput facets of the photonic integrated circuit. Bonding the photonicintegrated circuit to the cap may include bonding the plurality of inputfacets of the photonic integrated circuit against at least one opticalwindow in the cap positioned and oriented to allow beams of lightemitted from the plurality of laser diodes to exit the interior volume.Bonding the photonic integrated circuit to the cap may include bondingthe photonic integrated circuit to the cap to form at least one opticalwindow in the photonic integrated circuit positioned and oriented toallow beams of light emitted from the plurality of laser diodes to exitthe interior volume.

The method may further include providing a coupling between at least onelaser diode driver circuit and the plurality of laser diodes, inoperation the at least one laser diode driver circuit selectively drivescurrent to the laser diodes. Providing a coupling between at least onelaser diode driver circuit and the plurality of laser diodes mayinclude: bonding a plurality of electrical connections to the basesubstrate, each electrical connection coupled to a respective laserdiode in the plurality of laser diodes; providing a coupling betweeneach of the plurality of electrical connections and the at least onelaser diode driver circuit; and bonding an electrically insulating coverto the base substrate over the plurality of electrical connections, andbonding the cap to the base substrate may include bonding the cap to thebase substrate and the electrically insulating cover. Providing acoupling between each of the plurality of electrical connections and theat least one laser diode driver circuit may include: bonding a pluralityof electrical contacts to the base substrate, each electrical contactcoupled to a respective one of the plurality of electrical connections;and providing a coupling between each of the electrical contacts and theat least one laser diode driver circuit. Bonding the plurality of laserdiodes directly or indirectly to a base substrate may include bondingthe laser diodes directly or indirectly to a first surface of the basesubstrate, and bonding a cap to the base substrate may include bonding acap to the first surface of the base substrate, and the method mayfurther include bonding the at least one laser diode driver circuit to asecond surface of the base substrate, the second surface of the basesubstrate opposite the first surface of the base substrate. Bonding theplurality of laser diodes directly or indirectly to a base substrate mayinclude bonding the laser diodes directly or indirectly to a firstsurface of the base substrate, and bonding a cap to the base substratemay include bonding a cap to the first surface of the base substrate,and the method may further include bonding the at least one laser diodedriver circuit to the first surface of the base substrate.

Bonding a cap to the base substrate may include bonding a cap to thebase substrate using at least one of a seam welding process, a laserassisted soldering process, or a diffusion bonding process. The methodmay further include prior to bonding the cap to the base substrate,flooding the interior volume with an oxygen rich atmosphere. The methodmay further include positioning and orienting a collimation lens toreceive and collimate the aggregate beam of light from the outputcoupler of the photonic integrated circuit.

The method may further include laser writing the photonic integratedcircuit into writeable glass before bonding the photonic integratedcircuit to the cap. Laser writing the photonic integrated circuit intowriteable glass may include laser writing a plurality of waveguides intothe writeable glass, each waveguide of the plurality of waveguides beingwritten for a respective one laser diode of the plurality of laserdiodes. Laser writing a plurality of waveguides into the writeable glassmay include writing a waveguide combiner into the writeable glass.Writing a waveguide combiner into the writeable glass may includewriting at least one of: a directional coupler, Y-branch, whisperinggallery mode, or multi-mode interface coupler. Laser writing a pluralityof waveguides into the writeable glass may include laser writing eachwaveguide of the plurality of waveguide to have a input facet to receivelaser light from a respective laser diode of the plurality of laserdiodes and an output facet to output the received laser light, a spacingbetween the output facets of each waveguide being smaller than a spacingof the input facets of each waveguide. Laser writing the photonicintegrated circuit into writeable glass may include writing each inputfacet as a grating input coupler. Laser writing the photonic integratedcircuit in writeable glass may include writing each input facet as aplanar region with an index of refraction lower than an index ofrefraction of the writeable glass.

A method of manufacturing an optical engine may be summarized asincluding: bonding a plurality of laser diodes directly or indirectly toa base substrate; bonding a cap to the base substrate, the capcomprising at least one wall that, with the base substrate, defines aninterior volume sized and dimensioned to receive at least the pluralityof laser diodes, the cap being bonded to the base substrate to provide ahermetic or partially hermetic seal between the interior volume of thecap and a volume exterior to the cap; bonding writeable glass to thebase substrate; and after bonding the writeable glass to the basesubstrate, writing a photonic integrated circuit into the writeableglass, the photonic integrated circuit comprising a plurality of inputfacets and at least one output facet, in operation, the photonicintegrated circuit receives a plurality of beams of light at theplurality of input facets and wavelength multiplexes the plurality ofbeams of light to provide an aggregated beam of light at the at leastone output facet.

The method may further include: bonding each of the laser diodesindirectly to the base substrate by bonding each laser diode to arespective chip submount; and bonding each chip submount to the basesubstrate. Bonding each laser diode to a respective chip submount mayinclude bonding each laser diode to a respective chip submount using aeutectic gold tin (AuSn) solder process. Bonding each chip submount tothe base substrate may include step-soldering each chip submount to thebase substrate. Bonding each chip submount to the base substrate mayinclude bonding each chip submount to the base substrate using at leastone of a reflow oven process, thermosonic bonding, thermocompressionbonding, transient liquid phase (TLP) bonding, or laser soldering.Bonding each chip submount to the base substrate may include bonding achip submount that has a red laser diode bonded thereto, bonding a chipsubmount that has a green laser diode bonded thereto, bonding a chipsubmount that has a blue laser diode bonded thereto, and bonding a chipsubmount that has an infrared laser diode bonded thereto.

The method may further include bonding a plurality of collimation lensesbetween the plurality of laser diodes and the plurality of input facetsof the photonic integrated circuit, each of the plurality of collimationlenses positioned and oriented to collimate light received fromrespective ones of the beams of light emitted from the plurality oflaser diodes, and to output the collimated light toward the plurality ofinput facets of the photonic integrated circuit. Bonding the writeableglass to the cap may include bonding the writable glass against at leastone optical window in the cap positioned and oriented to allow beams oflight emitted from the plurality of laser diodes to exit the interiorvolume. Bonding the writeable glass to the cap may include bonding thewriteable glass to the cap to form at least one optical window in thewritable glass positioned and oriented to allow beams of light emittedfrom the plurality of laser diodes to exit the interior volume.

The method may further include providing a coupling between at least onelaser diode driver circuit and the plurality of laser diodes, inoperation the at least one laser diode driver circuit selectively drivescurrent to the laser diodes. Providing a coupling between at least onelaser diode driver circuit and the plurality of laser diodes mayinclude: bonding a plurality of electrical connections to the basesubstrate, each electrical connection coupled to a respective laserdiode in the plurality of laser diodes; providing a coupling betweeneach of the plurality of electrical connections and the at least onelaser diode driver circuit; and bonding an electrically insulating coverto the base substrate over the plurality of electrical connections, andbonding the cap to the base substrate may include bonding the cap to thebase substrate and the electrically insulating cover. Providing acoupling between each of the plurality of electrical connections and theat least one laser diode driver circuit may include: bonding a pluralityof electrical contacts to the base substrate, each electrical contactcoupled to a respective one of the plurality of electrical connections;and providing a coupling between each of the electrical contacts and theat least one laser diode driver circuit.

Bonding the plurality of laser diodes directly or indirectly to a basesubstrate may include bonding the laser diodes directly or indirectly toa first surface of the base substrate, and bonding a cap to the basesubstrate may include bonding a cap to the first surface of the basesubstrate, the method may further include bonding the at least one laserdiode driver circuit to a second surface of the base substrate, thesecond surface of the base substrate opposite the first surface of thebase substrate. Bonding the plurality of laser diodes directly orindirectly to a base substrate may include bonding the laser diodesdirectly or indirectly to a first surface of the base substrate, andbonding a cap to the base substrate may include bonding a cap to thefirst surface of the base substrate, the method may further includebonding the at least one laser diode driver circuit to the first surfaceof the base substrate.

Bonding a cap to the base substrate may include bonding a cap to thebase substrate using at least one of a seam welding process, a laserassisted soldering process, or a diffusion bonding process. The methodmay further include prior to bonding the cap to the base substrate,flooding the interior volume with an oxygen rich atmosphere. The methodmay further include positioning and orienting a collimation lens toreceive and collimate the aggregate beam of light from the at least oneoutput facet of the photonic integrated circuit.

Laser writing the photonic integrated circuit into the writeable glassmay include laser writing a plurality of waveguides into the writeableglass, each waveguide of the plurality of waveguides being written for arespective one laser diode of the plurality of laser diodes. Laserwriting a plurality of waveguides into the writeable glass may includewriting a waveguide combiner into the writeable glass. Writing awaveguide combiner into the writeable glass may include writing at leastone of: a directional coupler, Y-branch, whispering gallery mode, ormulti-mode interface coupler. Laser writing a plurality of waveguidesinto the writeable glass may include laser writing each waveguide of theplurality of waveguides to have an input facet to receive laser lightfrom a respective laser diode of the plurality of laser diodes and anoutput facet to output the received laser light, a spacing between theoutput facets of each waveguide being smaller than a spacing of theinput facets of each waveguide.

Laser writing the photonic integrated circuit into the writeable glassmay include writing each input facet as a grating input coupler. Laserwriting the photonic integrated circuit in the writeable glass mayinclude writing each input facet as a planar region with an index ofrefraction lower than an index of refraction of the writeable glass.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not necessarily drawn to scale, and some ofthese elements may be arbitrarily enlarged and positioned to improvedrawing legibility. Further, the particular shapes of the elements asdrawn, are not necessarily intended to convey any information regardingthe actual shape of the particular elements, and may have been solelyselected for ease of recognition in the drawings.

FIG. 1A is a left side, sectional elevational view of an optical engine,in accordance with the present systems, devices, and methods.

FIG. 1B is a front side, sectional elevational view of the opticalengine also shown in FIG. 1A, in accordance with the present systems,devices, and methods.

FIG. 2 is a flow diagram of a method of operating an optical engine, inaccordance with the present systems, devices, and methods.

FIG. 3 is a schematic diagram of a wearable heads-up display with alaser projector that includes an optical engine, and a transparentcombiner in a field of view of an eye of a user, in accordance with thepresent systems, devices, and methods.

FIG. 4 is an isometric view of a wearable heads-up display with a laserprojector that includes an optical engine, in accordance with thepresent systems, devices, and methods.

FIG. 5 is a flow diagram of a method of manufacturing an optical engine,in accordance with the present systems, devices, and methods.

FIG. 6 is a top plan view of a photonic integrated circuit forwavelength multiplexing that includes a plurality of grating couplers ona surface thereof, the photonic integrated circuit followed by a commoncollimation lens and an optional diffractive optical element, inaccordance with the present systems, devices, and methods.

FIG. 7 is a left side sectional elevational view of an optical enginethat includes a plurality of laser diodes inside a hermetically orpartially hermetically sealed package coupled to the photonic integratedcircuit for wavelength multiplexing, and a common collimation lens andan optional diffractive optical element, in accordance with the presentsystems, devices, and methods.

FIG. 8 is a schematic diagram of a laser writing system which can beused to write photonic integrated circuits in accordance with thepresent systems, devices, and methods.

FIG. 9 is a flow diagram of a method of manufacturing an optical engineincluding writing a photonic integrated circuit, in accordance with thepresent systems, devices, and methods.

FIGS. 10A and 10B are schematic diagrams of laser writing systems whichcan be used to write photonic integrated circuits in writeable glassalready bonded to a substrate or circuit, according to at least twoillustrated implementations.

FIGS. 11A and 11B are isometric views of optical engines including aninsulating cover which prevents undesired electrical signal transmissionfrom electrical connections, and showing implementations of opticalengines having differing positions for a laser diode driver circuit inaccordance with the present systems, devices, and methods.

FIG. 12A is a side sectional view of an optical engine that includes aplurality of laser diodes which output beams of light to a beam combinerwhich produces an aggregate beam.

FIG. 12B is a side sectional view of an optical engine havingcollimation lenses which redirect beams to a beam combiner which doesnot directly line up with outputs of laser diodes of the optical engine.

FIG. 12C is a side sectional view of an optical engine having acollimation lens which collimates an aggregate beam output from a beamcombiner.

FIG. 13 is an isometric view of a laser diode, showing a fast axis and aslow axis of a light beam generated by the laser diode, in accordancewith the present systems, devices, and methods.

FIG. 14A is a left side sectional view of a set of collimation lensesfor collimating a beam of light separately along different axes.

FIG. 14B is a top side sectional elevational view of the set ofcollimation lenses of FIG. 14A.

FIGS. 14C and 14D are isometric views of exemplary lens shapes whichcould be used as lenses in the implementation of FIGS. 14A and 14B.

FIG. 15A is a left side sectional view of a set of collimation lensesfor circularizing and collimating a beam of light.

FIG. 15B is a top side sectional elevational view of the set ofcollimation lenses of FIG. 15A.

FIGS. 15C and 15D are isometric views of exemplary lens shapes whichcould be used as a collimation lens in the implementation of FIGS. 15Aand 15B.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedimplementations. However, one skilled in the relevant art will recognizethat implementations may be practiced without one or more of thesespecific details, or with other methods, components, materials, etc. Inother instances, well-known structures associated with computer systems,server computers, and/or communications networks have not been shown ordescribed in detail to avoid unnecessarily obscuring descriptions of theimplementations.

Unless the context requires otherwise, throughout the specification andclaims that follow, the word “comprising” is synonymous with“including,” and is inclusive or open-ended (i.e., does not excludeadditional, unrecited elements or method acts).

Reference throughout this specification to “one implementation” or “animplementation” means that a particular feature, structure orcharacteristic described in connection with the implementation isincluded in at least one implementation. Thus, the appearances of thephrases “in one implementation” or “in an implementation” in variousplaces throughout this specification are not necessarily all referringto the same implementation. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more implementations.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its sense including “and/or” unless the contextclearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theimplementations.

One or more implementations of the present disclosure providelaser-based optical engines, for example, laser-based optical enginesfor laser projectors used in wearable heads-up displays or otherapplications. Generally, the optical engines discussed herein integratea plurality of laser dies or diodes (e.g., 3 laser diodes, 4 laserdiodes) within a single, hermetically or partially hermetically sealed,encapsulated package. As discussed further below with reference to FIGS.6, 7, and 10A, in at least some implementations, photonic integratedcircuits having grating couplers thereon may be used to wavelengthmultiplex beams of light emitted by the plurality of laser diodes into acoaxially superimposed aggregate beam. Alternatively, each wavelength oflight may be channeled individually through the photonic integratedcircuit. Such optical engines may have various advantages over existingdesigns including, for example, smaller volume, lower weight, bettermanufacturability, lower cost, faster modulation speed, etc. Thematerial used for the optical engines discussed herein may be anysuitable materials, e.g., ceramics with advantageous thermal properties,etc. As noted above, such features are particularly advantages invarious applications including WHUDs.

FIG. 1A is a left side, elevational sectional view of an optical engine100, which may also be referred to as a “multi-laser diode module” or an“RGB laser module,” in accordance with the present systems, devices, andmethods. FIG. 1B is a front side, elevational sectional view of theoptical engine 100. The optical engine 100 includes a base substrate 102having a top surface 104 and a bottom surface 106 opposite the topsurface. The base substrate 102 may be formed from a material that isradio frequency (RF) compatible and is suitable for hermetic sealing.For example, the base substrate 102 may be formed from low temperatureco-fired ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar®, otherceramics with suitable thermal properties, etc. The term Kovar®generally refers to iron-nickel-cobalt alloys having similar thermalexpansion coefficients to glass and ceramics, thus making Kovar®materials particularly suitable for forming hermetic seals which remainfunctional in a wide range of temperatures.

The optical engine 100 also includes a plurality of chip submounts 108a-108 d (collectively 108) bonded (e.g., attached) to the top surface104 of the base substrate 102. The plurality of chip submounts 108 arealigned in a row across a width of the optical engine 100 between theleft and right sides thereof. Each of the plurality of chip submounts108 includes a laser diode 110, also referred to as a laser chip orlaser die, bonded thereto. In particular, an infrared chip submount 108a carries an infrared laser diode 110 a, a red chip submount 108 bcarries a red laser diode 110 b, a green chip submount 108 c carries agreen laser diode 110 c, and a blue chip submount 108 d carries a bluelaser diode 110 d. In operation, the infrared laser diode 110 a providesinfrared laser light, the red laser diode 110 b provides red laserlight, the green laser diode 110 c provides green laser light, and theblue laser diode 110 d provides blue laser light. Each of the laserdiodes 110 may comprise one of an edge emitter laser or avertical-cavity surface-emitting laser (VCSEL), for example. Each of thefour laser diode/chip submount pairs may be referred to collectively asa “laser chip on submount,” or a laser CoS 112. Thus, the optical engine100 includes an infrared laser CoS 112 a, a red laser CoS 112 b, a greenlaser CoS 112 c, and a blue laser CoS 112 d. In at least someimplementations, one or more of the laser diodes 110 may be bondeddirectly to the base substrate 102 without use of a submount 108. Itshould be appreciated that although some implementations discussedherein describe laser diodes as chips or dies on submounts, other diesor types of devices, e.g., p-side down devices, may be used as well.

The optical engine 100 also includes a laser diode driver circuit 114bonded to the bottom surface 106 of the base substrate 102. The laserdiode driver circuit 114 is operatively coupled to the plurality oflaser diodes 110 via suitable electrical connections 116 to selectivelydrive current to the plurality of laser diodes. In at least someimplementations, the laser diode driver circuit 114 may be positionedrelative to the CoSs 112 to minimize the distance between the laserdiode driver circuit 114 and the CoSs 112. Although not shown in FIGS.1A and 1B, the laser diode driver circuit 114 may be operativelycoupleable to a controller (e.g., microcontroller, microprocessor, ASIC)which controls the operation of the laser diode driver circuit 114 toselectively modulate laser light emitted by the laser diodes 110. In atleast some implementations, the laser diode driver circuit 114 may bebonded to another portion of the base substrate 102, such as the topsurface 104 of the base substrate. In at least some implementations, thelaser diode driver circuitry 114 may be remotely located and operativelycoupled to the laser diodes 110. In order to not require the use ofimpedance matched transmission lines, the size scale may be smallcompared to a wavelength (e.g., lumped element regime), where theelectrical characteristics are described by (lumped) elements likeresistance, inductance, and capacitance.

Proximate the laser diodes 110 there is positioned an optical directorelement 118. Like the chip submounts 108, the optical director element118 is bonded to the top surface 104 of the base substrate 102. In theillustrated example, the optical director element 118 has a triangularprism shape that includes a plurality of planar faces. In particular theoptical director element 118 includes an angled front face 118 a thatextends along the width of the optical engine 100, a rear face 118 b, abottom face 118 c that is bonded to the top surface 104 of the basesubstrate 102, a left face 118 d, and a right face 118 e opposite theleft face. The optical director element 118 may comprise a mirror or aprism, for example.

The optical engine 100 also includes a cap 120 that includes a verticalsidewall 122 having a lower first end 124 and an upper second end 126opposite the first end. A flange 128 may be disposed around a perimeterof the sidewall 122 adjacent the lower first end 124. Proximate theupper second end 126 of the sidewall 122 there is a horizontal opticalwindow 130 that forms the “top” of the cap 120. The sidewall 122 and theoptical window 130 together define an interior volume 132 sized anddimensioned to receive the plurality of chip submounts 108, theplurality of laser diodes 110, and the optical director element 118. Thelower first end 124 and the flange 128 of the cap 120 are bonded to thebase substrate 102 to provide a hermetic or partially hermetic sealbetween the interior volume 132 of the cap and a volume 134 exterior tothe cap.

As shown best in FIG. 1A, the optical director element 118 is positionedand oriented to direct (e.g., reflect) laser light received from each ofthe plurality of laser diodes 108 upward (as shown) toward the opticalwindow 130 of the cap 120, wherein the laser light exits the interiorvolume 132.

The cap 120 may have a round shape, rectangular shape, or other shape.Thus, the vertical sidewall 122 may comprise a continuously curvedsidewall, a plurality (e.g., four) of adjacent planar portions, etc. Theoptical window 130 may comprise an entire top of the cap 120, or maycomprise only a portion thereof. In at least some implementations, theoptical window 130 may be located on the sidewall 122 rather thanpositioned as a top of the cap 120, and the laser diodes 110 and/or theoptical director element 118 may be positioned and oriented to directthe laser light from the laser diodes toward the optical window on thesidewall 122. At least some implementations may not include opticaldirector element 118 such that laser light from the laser diodes may beoutput towards the optical window on the sidewall 122 without the needfor intervening optical elements. In at least some implementations, thecap 120 may include a plurality of optical windows instead of a singleoptical window.

The optical engine 100 also includes four collimation/pointing lenses136 a-136 d (collectively 136), one for each of the four laser diodes110 a-110 d, respectively, that are bonded to a top surface 138 of theoptical window 130. Each of the plurality of collimation lenses 136 ispositioned and oriented to receive light from a corresponding one of thelaser diodes 110 through the optical window 130. In particular, thecollimation lens 136 a receives light from the infrared laser diode 110a via the optical director element 118 and the optical window 130, thecollimation lens 136 b receives light from the red laser diode 110 b viathe optical director element and the optical window, the collimationlens 136 c receives light from the green laser diode 110 c via theoptical director element and the optical window, and the collimationlens 136 d receives light from the blue laser diode 110 d via theoptical director element and the optical window.

Each of the collimation lenses 136 is operative to receive laser lightfrom a respective one of the laser diodes 110, and to generate a singlecolor beam. In particular, the collimation lens 136 a receives infraredlaser light from the infrared laser diode 110 a and produces an infraredlaser beam 138 a, the collimation lens 136 b receives red laser lightfrom the red laser diode 110 b and produces a red laser beam 138 b, thecollimation lens 136 c receives green laser light from the green laserdiode 110 c and produces a green laser beam 138 c, and the collimationlens 136 d receives blue laser light from the blue laser diode 110 d andproduces a blue laser beam 138 d.

The optical engine 100 may also include, or may be positioned proximateto, a beam combiner 140 that is positioned and oriented to combine thelight beams 138 a-138 d received from each of the collimation lenses 136into a single aggregate beam 142. As an example, the beam combiner 140may include one or more diffractive optical elements (DOE) and/orrefractive/reflective optical elements that combine the different colorbeams 138 a-138 d in order to achieve coaxial superposition. An examplebeam combiner is shown in FIG. 3 and discussed below.

In at least some implementations, the laser CoSs 112, the opticaldirector element 118, and/or the collimation lenses 136 may bepositioned differently. As noted above, laser diode driver circuit 114may be mounted on the top surface 104 or the bottom surface 106 of thebase substrate 102, depending on the RF design and other constraints(e.g., package size). In at least some implementations, the opticalengine 100 may not include the optical director element 118, and thelaser light may be directed from the laser diodes 110 toward thecollimation lenses 136 without requiring an intermediate opticaldirector element. Additionally, in at least some implementations, one ormore of the laser diodes may be mounted directly on the base substrate102 without use of a submount.

For the sake of a controlled atmosphere inside the interior volume 132,it may be desirable to have no organic compounds inside the interiorvolume 132. In at least some implementations, the components of theoptical engine 100 may be bonded together using no adhesives. In otherimplementations, a low amount of adhesives may be used to bond at leastone of the components, which may reduce cost while providing arelatively low risk of organic contamination for a determined lifetime(e.g., 2 or more years) of the optical engine 100. The use of adhesivesmay result in a partial hermetic seal, but this partial hermetic sealmay be acceptable in certain applications, as detailed below.

Generally, “hermetic” refers to a seal which is airtight, that is, aseal which excludes the passage of air, oxygen, and other gases.“Hermetic” within the present specification carries this meaning.Further, “partially hermetic” as used herein refers to a seal whichlimits, but does not necessarily completely prevent, the passage ofgases such as air. “Partially hermetic” as used herein may alternativelybe stated as “reduced hermiticity”. In the example above, adhesives maybe used to bond components. Such adhesives may result in a seal beingnot completely hermetic, in that some amount of gasses may slowly leakthrough the adhesive. However, such a seal can still be considered“partially hermetic” or as having “reduced hermiticity”, because theseal reduces the flow of gasses therethrough.

In one example application, even in an environment with only partialhermiticity, the life of laser diodes 110 and transparency of opticalwindow 130 may be maintained longer than the life of a battery of adevice, such that partial hermiticity may be acceptable for the devices.In some cases, even protecting interior volume 132 from particulate witha dust cover may be sufficient to maintain laser diodes 110 andtransparency of optical window 130 for the intended lifespan of thedevice. In some cases, laser diodes 110 and transparency of opticalwindow 130 may last for the intended lifespan of the device even withouta protective cover. Various bonding processes (e.g., attachingprocesses) for the optical engine 100 are discussed below with referenceto FIG. 5.

FIG. 2 is a flow diagram of a method 200 of operating an optical engine,in accordance with the present systems, devices, and methods. The method200 may be implemented using the optical engine 100 of FIGS. 1A-1B, forexample. It should be appreciated that methods of operating opticalengines according to the present disclosure may include fewer oradditional acts than set forth in the method 200. Further, the actsdiscussed below may be performed in an order different than the orderpresented herein.

At 202, at least one controller may cause a plurality of laser diodes ofan optical engine to generate laser light. As discussed above, theplurality of laser diodes may be hermetically or partially hermeticallysealed in an encapsulated package. The laser diodes may produce lightsequentially and/or simultaneously with each other. At 204, at least oneoptical director element may optionally receive the laser light from thelaser diodes. The optical director element may comprise a mirror or aprism, for example. As discussed above, in at least some implementationsthe optical engine may be designed such that laser light exits theoptical engine without use of an optical director element.

At 206, the at least one optical director element, if included, maydirect the received laser light toward an optical window of theencapsulated package. For example, the optical director element mayreflect the received laser light toward the optical window of theencapsulated package. In implementations without at least one opticaldirector element, the laser light generated by the plurality of laserdiodes may be output directly toward the optical window of theencapsulated package.

At 208, a plurality of collimation lenses may collimate the laser lightfrom the laser diodes that exits the encapsulated package via theoptical window to generate a plurality of differently colored laserlight beams. The collimation lenses may be positioned inside or outsideof the encapsulated package. As an example, the collimation lenses maybe physically coupled to the optical window of the encapsulated package.

At 210, a beam combiner may combine the plurality of laser light beamsreceived from each of the collimation lenses into a single aggregatebeam. The beam combiner may include one or more diffractive opticalelements (DOE) that combine different color beams in order to achievecoaxial superposition, for example. The beam combiner may include one ormore DOEs and/or one or more refractive/reflective optical elements. Anexample beam combiner is shown in FIG. 3 and discussed below.

FIG. 3 is a schematic diagram of a wearable heads-up display (WHUD) 300with an exemplary laser projector 302, and a transparent combiner 304 ina field of view of an eye 306 of a user of the WHUD, in accordance withthe present systems, devices, and methods. The WHUD 300 includes asupport structure (not shown), with the general shape and appearance ofan eyeglasses frame, carrying an eyeglass lens 308 with the transparentcombiner 304, and the laser projector 302.

The laser projector 302 comprises a controller or processor 310, anoptical engine 312 comprising four laser diodes 314 a, 314 b, 314 c, 314d (collectively 314) communicatively coupled to the processor 310, abeam combiner 316, and a scan mirror 318. The optical engine 312 may besimilar or identical to the optical engine 100 discussed above withreference to FIGS. 1A and 1B. Generally, the term “processor” refers tohardware circuitry, and may include any of microprocessors,microcontrollers, application specific integrated circuits (ASICs),digital signal processors (DSPs), programmable gate arrays (PGAs),and/or programmable logic controllers (PLCs), or any other integrated ornon-integrated circuit.

During operation of the WHUD 300, the processor 310 modulates lightoutput from the laser diodes 314, which includes a first red laser diode314 a (R), a second green laser diode 314 b (G), a third blue laserdiode 314 c (B), and a fourth infrared laser diode 314 d (IR). The firstlaser diode 314 a emits a first (e.g., red) light signal 320, the secondlaser diode 314 b emits a second (e.g., green) light signal 322, thethird laser diode 314 c emits a third (e.g., blue) light signal 324, andthe fourth laser diode 314 d emits a fourth (e.g., infrared) lightsignal 326. All four of light signals 320, 322, 324, and 326 enter orimpinge on the beam combiner 316. Beam combiner 316 could for example bebased on any of the beam combiners described in U.S. Provisional PatentApplication Ser. No. 62/438,725, U.S. Non-Provisional patent applicationSer. No. 15/848,265 (U.S. Publication Number 2018/0180885), U.S.Non-Provisional patent application Ser. No. 15/848,388 (U.S. PublicationNumber 2018/0180886), U.S. Provisional Patent Application Ser. No.62/450,218, U.S. Non-Provisional patent application Ser. No. 15/852,188(U.S. Publication Number 2018/0210215), U.S. Non-Provisional patentapplication Ser. No. 15/852,282, (U.S. Publication Number 2018/0210213),and/or U.S. Non-Provisional patent application Ser. No. 15/852,205 (U.S.Publication Number 2018/0210216).

In the illustrated example, the beam combiner 316 includes opticalelements 328, 330, 332, and 334. The first light signal 320 is emittedtowards the first optical element 328 and reflected by the first opticalelement 328 of the beam combiner 316 towards the second optical element330 of the beam combiner 316. The second light signal 322 is alsodirected towards the second optical element 330. The second opticalelement 330 is formed of a dichroic material that is transmissive of thered wavelength of the first light signal 320 and reflective of the greenwavelength of the second light signal 322. Therefore, the second opticalelement 330 transmits the first light signal 320 and reflects the secondlight signal 322. The second optical element 330 combines the firstlight signal 320 and the second light signal 322 into a single aggregatebeam (shown as separate beams for illustrative purposes) and routes theaggregate beam towards the third optical element 332 of the beamcombiner 316.

The third light signal 324 is also routed towards the third opticalelement 332. The third optical element 332 is formed of a dichroicmaterial that is transmissive of the wavelengths of light (e.g., red andgreen) in the aggregate beam comprising the first light signal 320 andthe second light signal 322 and reflective of the blue wavelength of thethird light signal 324. Accordingly, the third optical element 332transmits the aggregate beam comprising the first light signal 320 andthe second light signal 322 and reflects the third light signal 324. Inthis way, the third optical element 332 adds the third light signal 324to the aggregate beam such that the aggregate beam comprises the lightsignals 320, 322, and 324 (shown as separate beams for illustrativepurposes) and routes the aggregate beam towards the fourth opticalelement 334 in the beam combiner 316.

The fourth light signal 326 is also routed towards the fourth opticalelement 334. The fourth optical element 334 is formed of a dichroicmaterial that is transmissive of the visible wavelengths of light (e.g.,red, green, and blue) in the aggregate beam comprising the first lightsignal 320, the second light signal 322, and the third light signal 324and reflective of the infrared wavelength of the fourth light signal326. Accordingly, the fourth optical element 334 transmits the aggregatebeam comprising the first light signal 320, the second light signal 322,and the third light signal 324 and reflects the fourth light signal 326.In this way, the fourth optical element 334 adds the fourth light signal326 to the aggregate beam such that the aggregate beam 336 comprisesportions of the light signals 320, 322, 324, and 326. The fourth opticalelement 334 routes the aggregate beam 336 towards the controllable scanmirror 318.

The scan mirror 318 is controllably orientable and scans (e.g. rasterscans) the beam 336 to the eye 306 of the user of the WHUD 300. Inparticular, the controllable scan mirror 318 scans the laser light ontothe transparent combiner 304 carried by the eyeglass lens 308. The scanmirror 318 may be a single bi-axial scan mirror or two single-axis scanmirrors may be used to scan the laser light onto the transparentcombiner 304, for example. In at least some implementations, thetransparent combiner 304 may be a holographic combiner with at least oneholographic optical element. The transparent combiner 304 redirects thelaser light towards a field of view of the eye 306 of the user. Thelaser light redirected towards the eye 306 of the user may be collimatedby the transparent combiner 304, wherein the spot at the transparentcombiner 304 is approximately the same size and shape as the spot at theeye 306 of the user. The laser light may be converged by the eye 306 toa focal point at the retina of eye 306 and creates an image that isfocused. The visible light may create display content in the field ofview of the user, and the infrared light may illuminate the eye 306 ofthe user for the purpose of eye tracking.

FIG. 4 is a schematic diagram of a wearable heads-up display (WHUD) 400with a laser projector 402 in accordance with the present systems,devices, and methods. WHUD 400 includes a support structure 404 with theshape and appearance of a pair of eyeglasses that in use is worn on thehead of the user. The support structure 404 carries multiple components,including eyeglass lens 406, a transparent combiner 408, the laserprojector 402, and a controller or processor 410. The laser projector402 may be similar or identical to the laser projector 302 of FIG. 3.For example, the laser projector 402 may include an optical engine, suchas the optical engine 100 or the optical engine 312. The laser projector402 may be communicatively coupled to the controller 410 (e.g.,microprocessor) which controls the operation of the projector 402, asdiscussed above. The controller 410 may include or may becommunicatively coupled to a non-transitory processor-readable storagemedium (e.g., memory circuits such as ROM, RAM, FLASH, EEPROM, memoryregisters, magnetic disks, optical disks, other storage), and thecontroller may execute data and/or instruction from the non-transitoryprocessor readable storage medium to control the operation of the laserprojector 402.

In operation of the WHUD 400, the controller 410 controls the laserprojector 402 to emit laser light. As discussed above with reference toFIG. 3, the laser projector 402 generates and directs an aggregate beam(e.g., aggregate beam 336 of FIG. 3) toward the transparent combiner 408via at least one controllable mirror (not shown in FIG. 4). Theaggregate beam is directed towards a field of view of an eye of a userby the transparent combiner 408. The transparent combiner 408 maycollimate the aggregate beam such that the spot of the laser lightincident on the eye of the user is at least approximately the same sizeand shape as the spot at transparent combiner 408. The transparentcombiner 408 may be a holographic combiner that includes at least oneholographic optical element.

FIG. 5 is a flow diagram of a method 500 of manufacturing an opticalengine, in accordance with the present systems, devices, and methods.The method 500 may be implemented to manufacture the optical engine 100of FIGS. 1A-1B or the optical engine 312 of FIG. 3, for example. Itshould be appreciated that methods of manufacturing optical enginesaccording to the present disclosure may include fewer or additional actsthan set forth in the method 500. Further, the acts discussed below maybe performed in an order different than the order presented herein.

At 502, a plurality of laser diodes may be bonded to a respectiveplurality of submounts. In at least some implementations, this methodmay be performed by an entity different than that manufacturing theoptical engine. For example, in at least some implementations, one ormore of the plurality of laser diodes (e.g., green laser diode, bluelaser diode) may be purchased as already assembled laser CoSs. For easeof handling and simplification of the overall process, in at least someimplementations it may be advantageous to also bond laser diodes thatcannot be procured on submounts to a submount as well. As a non-limitingexample, in at least some implementations, one or more of the laserdiodes may be bonded to a corresponding submount using an eutectic goldtin (AuSn) solder process, which is flux-free and requires heating uptop 280° C.

At 504, the plurality of CoSs may be bonded to a base substrate.Alternatively, act 502 could be skipped for at least one or all of thelaser diodes, and act 504 could comprise bonding the at least one or allof the laser diodes directly to the base substrate. The base substratemay be formed from a material that is RF compatible and is suitable forhermetic sealing. For example, the base substrate may be formed from lowtemperature co-fired ceramic (LTCC), aluminum nitride (AlN), alumina,Kovar®, etc. Since several CoSs are bonded next to each other on thesame base substrate, it may be advantageous to either “step-solder” themsequentially or to use a bonding technique that does not rely onre-melting of solder materials. For step-soldering, each subsequentsoldering step utilizes a process temperature that is less than theprocess temperatures of previous solder steps to prevent re-melting ofsolder materials. It may also be important that the laserdiode-to-submount bonding does not re-melt during bonding of the CoSs tothe base substrate. Bonding technologies other than step-soldering thatmay be used include parallel soldering of all CoS in reflow ovenprocess, thermosonic or thermocompression bonding, transient liquidphase (TLP) bonding, laser soldering, etc. Some of these example bondingtechnologies are discussed below.

For parallel soldering of all CoSs in a reflow oven process, appropriatetooling is required to assure proper bonding and alignment during theprocess. An advantage of this process is the parallel and hence timeefficient bonding of all CoSs at once and even many assemblies inparallel. A possible disadvantage of this process is the potential lossof the alignment of components during the reflow process. Generally, asoldering cycle ideally needs a few minutes of dwell time. Preheatingmay be used to reduce the soldering time, which requires a few minutesfor such a process depending on the thermal mass of the components beingbonded. Thus, a batch process may be used with regular soldering toreduce the assembly costs with high throughput at the expense ofalignment tolerance.

For thermosonic or thermocompression bonding, thick gold metallizationmay be used but no extra solder layer is required. The temperatures forthermocompression bonding might be as high as 300 to 350° C. to have agood bond with a good thermal conductivity. Thermosonic bonding may beused to reduce the pressure and temperature needed for bonding, whichmay be required for at least some components that might not tolerate thetemperatures required for thermocompression bonding.

Transient liquid phase (TLP) bonding may also be used. There are manydifferent reaction couples that may be used, including gold-tin,copper-tin, etc. With this method, a liquid phase is formed during thebonding which will solidify at the same temperature. The re-meltingtemperatures of the bond are much higher than the solderingtemperatures.

In at least some implementations, laser soldering may be used to bondsome or all of the components of the optical engine. Generally, thethermal characteristic of the parts to be bonded may be important whenimplementing a laser soldering process.

Subsequent reflows of solder are not recommended due to liquid phasereaction or dissolution mechanisms which may reduce the reliability ofthe joint. This could result in voiding at the interface or a reductionin strength of the joint itself. In order to mitigate potential reflowdissolution problems, other options can be taken into consideration,which do not rely on extreme heating of the device and can be favorablein terms of production cost. For example, bonding of the base substratewith adhesives (electrically conductive for common mass, ornon-conductive for floating) may be acceptable with respect to heattransfer and out-gassing as discussed regarding partial hermetic sealingabove.

Further, in at least some implementations, a reactive multi-layer foilmaterial (e.g., NanoFoil®) or a similar material may be used as a solderpre-form, which enables localized heat transfer. A reactive multi-layerfoil material is a metallic material based on a plurality (e.g.,hundreds, thousands) of reactive foils (aluminum and nickel) thatenables die-attach soldering (e.g., silicon chip onto stainless steelpart). In such implementations, dedicated heat transfer supportmetallizations may be deposited onto the two components being joinedtogether. This method may be more advantageous for CoS-to-base substratemounting compared to chip-to-submount bonding. Generally, bonding usingreactive multi-layer foil materials enables furnace-free,low-temperature soldering of transparent or non-transparent components,without reaching the bonding temperatures for solder reflow processes.Reactive multi-layer foil materials can be patterned with a ps-laserinto exact preform shapes.

At 506, the optical director element, if included, may be bonded to thebase substrate proximate the laser CoSs. The optical director elementmay be bonded to the base substrate using any suitable bonding process,including the bonding processes discussed above with reference to act504.

At 508, the laser diode driver circuit may optionally be bonded to thebase substrate. As noted above, the laser diode driver circuit may bebonded to the base substrate such that the distance between the laserdiode driver circuit and the laser CoSs is minimized. This may alsocomprise positioning a plurality of electrical connections whichoperatively couple the laser diode driver circuit to the plurality oflaser diodes as shown in FIGS. 11A and 11B. In alternativeimplementations, the laser diode driver circuit may be bonded to aseparate base substrate from the other components mentioned above asshown in FIG. 11B. The process used to bond the laser diode drivercircuit to the base substrate may be any suitable bonding process, suchas bonding processes commonly used to bond surface mount devices (SMD)to circuit boards. In other alternative implementations, the laser diodedriver circuit may be mounted directly to a frame of a WHUD. Forimplementations where the laser diode drive circuit is not bonded to thesame base substrate as the other components mentioned above, a pluralityof electrical contacts and electrical connections could be bonded to thebase substrate, each electrical connection operatively connecting arespective electrical contact to a respective laser diode. Subsequently,the at least one laser driver circuit could be operatively coupled tothe electrical contacts, which will then electrically couple the laserdiode drive circuit to the electrical connections and consequently tothe laser diodes. Exemplary arrangements of electrical connections andelectrical contacts is discussed later with reference to FIG. 11B.

At 510, the cap may be bonded to the base substrate to form a hermeticor partially hermetic seal between the interior volume of theencapsulated package and an exterior environment. As noted above, it maybe desirable to maintain a specific atmosphere for the laser diode chipsfor reliability reasons. In at least some implementations, adhesivesealing may be undesirable because of the high permeability of gases.This is especially the case for blue laser diodes, which emit blue laserlight that may bake contamination on facets and windows, therebyreducing transparency of the optical window. However, as detailed aboveregarding FIGS. 1A and 1B, partial hermeticity, a particulate dustcover, or even no protective cover may be acceptable for certainapplications. In implementations where the cap would be bonded overelectrical connections which connect the at least one laser diode drivercircuit to the plurality of laser diodes, such as when the at least onelaser diode driver circuit is bonded to the same side of a basesubstrate as the laser diodes, or when the at least one laser diodedriver circuit is coupled to electrical contacts bonded to the same sideof the base substrate as the laser diodes, an electrically insulatingcover can first be bonded to the base substrate over the electricalconnections. Subsequently, the cap can be bonded at least partially tothe electrically insulating cover, and potentially to a portion of thebase substrate if the insulating cover does not fully encircle theintended interior volume. In this way, at least a portion of the capwill be bonded to the base substrate indirectly by being bonded to theelectrically insulating cover. In some implementations, the entire capcould be bonded to the base substrate indirectly by being bonded to anelectrically insulating cover which encircles the intended interiorvolume. Exemplary electrically insulating covers are discussed laterwith reference to FIGS. 11A and 11B.

During the sealing process, the atmosphere may be defined by floodingthe package accordingly. For example, the interior volume of theencapsulated package may be flooded with an oxygen enriched atmospherethat burns off contaminants which tend to form on interfaces where thelaser beam is present. The sealing itself may also be performed so as toprevent the exchange between the package atmosphere and the environment.Due to limitations concerning the allowed sealing temperature, e.g., thecomponents inside the package should not be influenced, in at least someimplementations seam welding or laser assisted soldering/diffusionbonding may be used. In at least some implementations, localized sealingusing a combination of seam welding and laser soldering may be used.

At 512, the collimation lenses may be actively aligned. For example,once the laser diode driver circuit has been bonded and the cap has beensealed, the laser diodes can be turned on and the collimations lensesfor each laser diode can be actively aligned. In at least someimplementations, each of the collimation lenses may be positioned tooptimize spot as well as pointing for each of the respective laserdiodes.

At 514, the beam combiner may be positioned to receive and combineindividual laser beams into an aggregate beam. As discussed above, thebeam combiner may include one or more diffractive optical elementsand/or one or more refractive/reflective optical elements that functionto combine the different color beams into an aggregate beam. Theaggregate beam may be provided to other components or modules, such as ascan mirror of a laser projector, etc.

FIG. 6 is a top plan view of a photonic integrated circuit 600 forwavelength multiplexing followed by a common collimation lens 602 and anoptional diffractive optical element 604. The photonic integratedcircuit 600 may be a component in an optical engine, such as an opticalengine 700 of FIG. 7, an optical engine 1000 a of FIG. 10A, or anoptical engine 1000 b of FIG. 10B discussed further below. The photonicintegrated circuit 600 includes a plurality of input facets 612 a-612 dand at least one output facet 608 (e.g., output optical coupler orgrating output coupler). In FIG. 6, input facets 612 a-612 d are shownas grating couplers (also referred to as “diffractive grating couplers”or “grating input couplers”) on a top surface 606 thereof, but otherinput facets are possible such as illustrated in FIG. 10B discussedbelow. In operation, the photonic integrated circuit 600 receives aplurality of beams of light 610 a-610 d that are coupled to the photonicintegrated circuit via the input facets 612 a-612 d, respectively, andwavelength multiplexes the plurality of beams to provide a coaxiallysuperimposed aggregate beam of light 614 that exits the photonicintegrated circuit at the output facet 608, output optical coupler orgrating output coupler. Compared to edge coupling, in at least someapplications using grating input couplers for input facets 612 a-612 dmay allow for relaxed tolerances for beam alignment. Generally, thephotonic integrated circuit 600 may include one or more diffractiveoptical elements (DOE) and/or refractive/reflective optical elementsthat combine the different color beams 610 a-610 d in order to achievecoaxial superposition.

Following out-coupling of the aggregate beam 614 from the output facet608 of the photonic integrated circuit 600, the aggregated beam iscollimated via the common collimation lens 602. In at least someimplementations, the collimation lens 602 may be either an achromaticlens or an apochromatic lens (or lens assemblies), depending on theparticular optical design and tolerances of the system. In at least someimplementations, one or more diffractive optical elements 604 may beused to provide wavelength dependent focus correction.

FIG. 7 is a left side sectional elevational view of the optical engine700. The optical engine 700 includes several components that may besimilar or identical to the components of the optical engine 100 ofFIGS. 1A and 1B. Thus, some or all of the discussion above may beapplicable to the optical engine 700.

The optical engine 700 includes a base substrate 702 having a topsurface 704 and a bottom surface 706 opposite the top surface. The basesubstrate 702 may be formed from a material that is radio frequency (RF)compatible and is suitable for hermetic sealing. For example, the basesubstrate 702 may be formed from low temperature co-fired ceramic(LTCC), aluminum nitride (AlN), alumina, Kovar®, etc.

The optical engine 700 also includes a plurality of chip submounts 708(only one chip submount visible in the sectional view of FIG. 7) thatare bonded (e.g., attached) to the top surface 704 of the base substrate702. The plurality of chip submounts 708 are aligned in a row across awidth of the optical engine 700 between the left and right sidesthereof. Each of the plurality of chip submounts 708 includes a laserdiode 710, also referred to as a laser chip or laser die, bondedthereto. In particular, an infrared chip submount carries an infraredlaser diode, a red chip submount carries a red laser diode, a green chipsubmount carries a green laser diode, and a blue chip submount carries ablue laser diode. In operation, the infrared laser diode providesinfrared laser light, the red laser diode provides red laser light, thegreen laser diode provides green laser light, and the blue laser diodeprovides blue laser light. Each of the laser diodes 710 may comprise oneof an edge emitter laser or a vertical-cavity surface-emitting laser(VCSEL), for example. Each of the four laser diode/chip submount pairsmay be referred to collectively as a “laser chip on submount,” or alaser CoS 712. Thus, the optical engine 700 includes an infrared laserCoS, a red laser CoS, a green laser CoS, and a blue laser CoS. In atleast some implementations, one or more of the laser diodes 710 may bebonded directly to the base substrate 702 without use of a submount 708.

The optical engine 700 also includes a laser diode driver circuit 714bonded to the bottom surface 706 of the base substrate 702. The laserdiode driver circuit 714 is operatively coupled to the plurality oflaser diodes 710 via suitable electrical connections 716 to selectivelydrive current to the plurality of laser diodes. Generally, the laserdiode driver circuit 714 may be positioned relative to the CoSs 712 tominimize the distance between the laser diode driver circuit 714 and theCoSs 712. Although not shown in FIG. 7, the laser diode driver circuit714 may be operatively coupleable to a controller (e.g.,microcontroller, microprocessor, ASIC) that controls the operation ofthe laser diode driver circuit 714 to selectively modulate laser lightemitted by the laser diodes 710. In at least some implementations, thelaser diode driver circuit 714 may be bonded to another portion of thebase substrate 702, such as the top surface 704 of the base substrate,similar to the implementations shown in FIGS. 11B and 11C. In at leastsome implementations, the laser diode driver circuitry 714 may beremotely located and operatively coupled to the laser diodes 710. Inorder to not require the use of impedance matched transmission lines,the size scale may be small compared to a wavelength (e.g., lumpedelement regime), where the electrical characteristics are described by(lumped) elements like resistance, inductance, and capacitance.

Proximate the laser diodes 710 there is positioned an optical directorelement 718. Like the chip submounts 708, the optical director element718 is bonded to the top surface 704 of the base substrate 702. In theillustrated example, the optical director element 718 has a triangularprism shape that includes a plurality of planar faces. In particular theoptical director element 718 includes an angled front face 718 a thatextends along the width of the optical engine 700, a rear face 718 b, abottom face 718 c that is bonded to the top surface 704 of the basesubstrate 702, a left face 718 d, and a right face 718 e opposite theleft face. The optical director element 718 may comprise a mirror or aprism, for example. In at least some implementations, the angled frontface 718 a may be curved to provide fast axis collimation of the laserlight from the laser diodes 710.

The optical engine 700 also includes a cap 720 that includes a verticalsidewall 722 having a lower first end 724 and an upper second end 726opposite the first end. A flange 728 may be disposed around a perimeterof the sidewall 722 adjacent the lower first end 724. Proximate theupper second end 726 there of the sidewall 722 there is a horizontal (asshown) optical window 730 that forms the “top” of the cap 120. Thesidewall 722 and the optical window 730, along with a portion of the topsurface 704 of the base substrate 702, together define an interiorvolume 732 sized and dimensioned to receive the plurality of chipsubmounts 708, the plurality of laser diodes 710, and the opticaldirector element 717. The lower first end 724 and the flange 728 of thecap 720 are bonded to the base substrate 702 to provide a hermetic orpartially hermetic seal between the interior volume 732 of the cap and avolume 734 exterior to the cap.

The optical director element 718 is positioned and oriented to direct(e.g., reflect) laser light received from each of the plurality of laserdiodes 710 upward (as shown) toward the optical window 730 of the cap720, wherein the laser light exits the interior volume 732.

The cap 720 may have a round shape, rectangular shape, or other shape.Thus, the vertical sidewall 722 may comprise a continuously curvedsidewall, a plurality (e.g., four) of adjacent planar portions, etc. Theoptical window 730 may comprise an entire top of the cap 720, or maycomprise only a portion thereof. In at least some implementations, theoptical window 730 may be located on the sidewall 722 rather thanpositioned as a top of the cap 720, and the laser diodes 710 and/or theoptical director element 718 (if present) may be positioned and orientedto direct the laser light from the laser diodes toward the opticalwindow on the sidewall 722. In at least some implementations, the cap720 may include a plurality of optical windows instead of a singleoptical window 730.

In at least some implementations, the optical engine 700 optionallyincludes four collimation lenses 736 (only one visible in the sectionalview of FIG. 7), one for each of the four laser diodes 710. In otherimplementations, the collimation lenses 736 are omitted. In theillustrated implementation, the collimation lenses 736 are bonded to abottom surface of the optical window 730 in a row, although thecollimation lenses may be positioned differently in otherimplementations. For example, in at least some implementations, thecollimation lenses 736 may be positioned outside of the package (e.g.,outside of the interior volume 732) rather than inside the package asshown in FIG. 7. Each of the plurality of collimation lenses 736 may bepositioned and oriented to receive light from a corresponding one of thelaser diodes 710, and to direct collimated light upward (as shown)through the optical window 730 toward the photonic integrated circuit600, which is shown “inverted” in FIG. 7 (relative to FIG. 6) so thatthe input facets 612 a-612 d (collectively, 612) on the surface 606 ofthe photonic integrated circuit face a top surface 738 of the opticalwindow 730 of the cap 720.

The optical director element 718 and the collimation lenses 736 (whenpresent) direct the beams of light 610 a-610 d (see FIG. 6) into thephotonic integrated circuit 600 via the input facets 612 a-612 d. Thephotonic integrated circuit 600 may be bonded to the top surface of theoptical window 730, as shown in FIG. 7. In at least someimplementations, the photonic integrated circuit 600 may be bonded tothe top surface 704 of the base substrate 702 instead. As discussedabove, in operation, the photonic integrated circuit 600 receives aplurality of beams of light 610 a-610 d via the inputs facets 612 a-612d (e.g. grating couplers), respectively, and wavelength multiplexes theplurality of beams to provide a coaxially superimposed aggregate beam oflight 614 that exits the photonic integrated circuit at the outputoptical coupler 608.

In at least some implementations, the laser diodes 710 may be directlycoupled to the photonic integrated circuit 600. In such implementations,the laser diodes 710 may be positioned immediately adjacent to awaveguide structure (e.g., photonic integrated circuit or otherwaveguide structure) such that sufficient coupling (e.g., acceptableinsertion loss) is achieved. For example, in at least someimplementations, the photonic integrated circuit 600 may function as theoptical window of the package itself.

Following out-coupling of the aggregate beam 614 from the output facet608 of the photonic integrated circuit 600, the aggregated beam may becollimated via the common collimation lens 602. In at least someimplementations, the common collimation lens 602 may be bonded to thetop surface 704 proximate the photonic integrated circuit 600. In atleast some implementations, the collimation lens 602 may be either anachromatic lens or an apochromatic lens, depending on the particularoptical design and tolerances of the system. In at least someimplementations, the optical engine 700 may include one or morediffractive optical elements 604 to provide wavelength dependent focuscorrection.

In at least some implementations, at least some of the components may bepositioned differently. As noted above, the laser diode driver circuit714 may be mounted on the top surface 704 or the bottom surface 706 ofthe base substrate 702, or may be positioned remotely therefrom,depending on the RF design and other constraints (e.g., package size),similarly to as discussed with reference to FIGS. 11A and 11B below. Inat least some implementations, the optical engine 700 may not include anoptical director element (e.g., optical director element 718 of FIG. 7),and the laser light may be directed from the laser diodes 710 toward theoptical window 730 directly, such as if the laser diodes are VCSEL laserdiodes as discussed with reference to FIGS. 12A-12C below, with ourwithout collimation lenses 736. Additionally, in at least someimplementations, one or more of the laser diodes 710 may be mounteddirectly on the base substrate 702 without use of a submount. Further,in at least some implementations, in the case of an inorganic oracceptably organic waveguide (e.g., photonic integrated circuit),coupling may be accomplished inside the encapsulated package. Suchfeature eliminates the requirement for a separate window, as thewaveguide 600 services as the window (e.g., optical window 730). In suchimplementations, the plurality of grating couplers of the photonicintegrated circuit may be positioned inside the interior volume of theencapsulated package and the at least one optical output coupler of thephotonic integrated circuit may be positioned outside of the interiorvolume, for example.

For the sake of a controlled atmosphere inside the interior volume 732,it may be desirable to have no organic compounds inside the interiorvolume 732. In at least some implementations, the components of theoptical engine 700 may be bonded together using no adhesives. In otherimplementations, a low amount of adhesives may be used to bond at leastone of the components, which may reduce cost while providing arelatively low risk of organic contamination for a determined lifetime(e.g., 2 or more years) of the optical engine 700. Similarly to asdetailed above regarding FIGS. 1A and 1B, partial hermeticity, aparticulate dust cover, or even no protective cover may be acceptablefor certain applications. Various bonding processes (e.g., attachingprocesses) for the optical engine 700 are discussed above with referenceto FIG. 5.

In at least some implementations, the collimation lenses 736 (whenpresent) and the collimation lens 602 may be actively aligned. In atleast some implementations, the CoSs 712, the cap 720 (including opticalwindow 730), and/or the photonic integrated circuit 600 may be passivelyaligned. Further, depending on the particular design, it may beadvantageous to utilize a smaller base substrate 702 and use anadditional carrier substrate instead.

FIG. 8 is a schematic diagram of a laser writing system 800 inaccordance with the present systems, designs and methods. Laser writingsystem 800 comprises at least writing laser 810, focusing optic 812,writeable glass 820 and translatable mount 830. Although the term“glass” is used herein for convenience, any appropriate laser-writablematerial could be used in place of writeable glass 820. Writing laser810 emits laser light 811. Laser light 811 comprises short (femptosecondand/or picosecond length) pulses of laser light; consequently, laserlight 811 has extremely high peak instantaneous power. Focusing optic812 focuses laser light 811 to focal point 813. Writeable glass 820 maycomprise a contiguous piece of glass or similar transparent material,which is typically transparent to the laser light 811 emitted by thewriting laser 810; in other words the light emitted by the writing lasergenerally will not be absorbed by the glass via typical (linear) opticalprocesses. At the focal point 813, the intensity of laser light 811 isvery high due to the combination of spatial focusing (focusing the beamof writing laser light 811 to a small point 813) and temporal focusing(emitting the laser light 811 as extremely short femptosecond orpicosecond pulses). The high intensity of light at the focal point 813allows nonlinear optical processes such as multiphoton absorption,avalanche ionization, Coulomb collisions (causing lattice ionization andbreakdown), and heat conduction to occur in the writeable glass 820,absorbing the light and changing the refractive index of the glass. Thechange in refractive index may be a positive increase in refractiveindex.

Writeable glass 820 can be physically coupled to translatable mount 830,such as by using clamps 821, adhesive, or any other appropriate couplingmechanism. Such coupling mechanism is preferably removable, such thatwriteable glass 820 can be detached from translatable mount 830 afterlaser writing is complete. Translation of translatable mount 830 in theX, Y, and/or Z direction will result in corresponding translation ofwriteable glass 820, moving the location of focal point 813 withinwriteable glass 820. Translating the writeable glass 820 relative tofocal point 813 can create a region of changed refractive index in thewriteable glass 820. An increased refractive index in this region causesany light channeled therethrough to experience total internalreflection, thus forming waveguide 822. In other words, waveguide 822can be formed as a continuous path of increased refractive index withinwriteable glass 820 created by laser light 811 at focal point 813.

The technique of FIG. 8 can be used to laser write at least onewaveguide into writeable glass 820. For example, a photonic integratedcircuit could be written, such as photonic integrated circuit 600described with regards to FIG. 6. Inputs facets 612 a, 612 b, 612 c, and612 d (such as grating couplers) could also be written using thistechnique.

Writing at least one waveguide may include writing an individualwaveguide for each wavelength of light impinging on the writeable glass820, where each waveguide comprises a respective input facet (such as aninput grating coupler) and a respective output facet. Each output facetmay be positioned to provide light to other components or modules, suchas a scan mirror of a laser projector, etc. In one implementation, fourwaveguides could be written into writeable glass 820, one waveguide foreach beam of light 610 a, 610 b, 610 c, and 610 d. Four grating couplerscould also be written, one for each waveguide.

Writing at least one waveguide may include writing a waveguide combiner,wherein the waveguide combiner combines individual laser beams into acoaxially superimposed aggregate beam. Writing a waveguide combiner mayinclude writing at least one: directional coupler (DC), Y-branch,whispering gallery mode coupler, or multi-mode interference coupler. Theaggregate beam may be provided to other components or modules, such as ascan mirror of a laser projector, etc.

In other implementations, the photonic integrated circuit 600 mayinclude one or more diffractive optical elements (DOE) and/orrefractive/reflective optical elements that combine the different colorbeams 610 a-d in order to achieve coaxial superposition.

Alternatively, instead of writing a waveguide combiner, individualwaveguides could be written which do not strictly coaxially superimposethe beams of light, but instead bring each beam of light close together.That is, the input facet (e.g. grating coupler) for each waveguide inthe photonic integrated circuit can be positioned relatively far fromthe other input facets, to receive laser light from a respective laserdiode, but the output facets for each of the waveguides can bepositioned relatively close together. In other words, a spacing betweenthe output facets of each waveguide can be smaller than a spacing of theinput facets of each waveguide. In such an implementation, eachwaveguide can be optimized for performance with light of a correspondingwavelength, for example to ensure that each wavelength of light exitsthe photonic integrated circuit with the same divergence angle as eachother wavelength. The output of each individual waveguide can be placedclose enough together (on the order of 10s of microns) such that thatthe light output by each individual waveguide may still follow the sameoptical path through the rest of a projector, display, or WHUD assemblywhere the photonic integrated circuit is implemented.

FIG. 9 is a flow diagram of a method 900 of manufacturing an opticalengine, in accordance with the present systems, devices, and methods.The method 900 may be implemented to manufacture the optical engine 700of FIG. 7, for example. It should be appreciated that methods ofmanufacturing optical engines according to the present disclosure mayinclude fewer or additional acts than set forth in the method 900.Further, the acts discussed below may be performed in an order differentthan the order presented herein.

Method 900 can include at least acts 902, 904, 906, 908, 910, 912, 914,and 916. Acts 902, 904, 906, 908, and 910 substantially correspond toacts 502, 504, 506, 508, and 510, respectively, of method 500 in FIG. 5,such that the disclosure of these acts with reference to FIG. 5 is alsoapplicable to FIG. 9. As such, the details of these acts in FIG. 9 willnot be repeated in the interests of brevity.

At 912, a photonic integrated circuit is laser written in writeableglass, using for example the techniques described with regards to FIG.8. The photonic integrated circuit may be similar to photonic integratedcircuit 600 described with reference to FIG. 6. Specifically, thephotonic integrated circuit can include at least one input facet and atleast one output facet. In operation, the photonic integrated circuitcan receive a plurality of beams of light that are coupled to thephotonic integrated circuit at a plurality of input facets (e.g. gratingcouplers), and wavelength multiplex the plurality of beams of light toprovide a coaxially superimposed aggregate beam of light that exits thephotonic integrated circuit at the output facet. Alternatively, inoperation, the photonic integrated circuit can receive a plurality ofbeams of light that are coupled to the photonic integrated circuit at aplurality of input facets (e.g. grating couplers), redirect theplurality of beams of light to exit the photonic integrated circuit at aplurality of spatially close output facets.

At 914, the writeable glass including the photonic integrated circuit isbonded to the cap. Any appropriate bonding technique may be used,including those described with reference to acts 502, 504, 506, 508, and510 in FIG. 5. In some implementations, the photonic integrated circuitmay be positioned against an optical window of the cap, such that laserlight from the laser diodes may pass through the optical window directlyinto the input facets of the photonic integrated circuit. Alternatively,the photonic integrated circuit may be positioned directly against thecap, such that the photonic integrated circuit acts as the opticalwindow, and laser light from the laser diodes may directly enter theinput facets of the photonic integrated circuit.

In order for light to travel through a photonic integrated circuit, thelight emitted by each laser diode should preferably be aligned with arespective input facet of the photonic integrated circuit with highprecision; mis-alignment of greater than 10 micrometers maysignificantly reduce the efficiency of the photonic integrated circuit.An output facet of each laser diode may have dimensions smaller thanfour square micrometers; aligning such small components to such highprecision presents a non-trivial technical challenge.

In one implementation, each input facet of the photonic integratecircuit could be written as a grating coupler as shown in FIG. 6, whichincreases the tolerances for misalignment.

In act 916, a collimation lens may be provided such that a coaxiallysuperimposed beam of light from the output edge of the photonicintegrated circuit will be collimated by the collimation lens. Thecollimation lens may optionally optimize the spot (e.g., circularize)the coaxially superimposed beam. In some implementations, more than onecollimation lens may be provided if the light output from the photonicintegrated circuit is not a fully coaxially superimposed beam. Thecollimation lens or lenses may be actively aligned after the othercomponents are assembled, or may be passively aligned such thatappropriate alignment is achieved during assembly.

As mentioned above, aligning a photonic integrated circuit such thateach input facet of the photonic integrated circuit lines up with a beamof light emitted by each laser diode with high-precision presents anon-trivial challenge. The present systems, devices, and methods providea solution to this challenge, by producing photonic integrated circuitswhere the fabrication process includes an alignment process, obviatingthe need for a later mechanical alignment process, as discussed belowwith reference to FIG. 10. Direct laser writing (DLW) as disclosedherein is a process by which photonic integrated circuits may befabricated with high precision that allows for intrinsic alignment.

FIG. 10A is a left side sectional view of photonic integrated circuitwriting system 1000 a. Photonic integrated circuit writing system 1000 aincludes components that may be substantively similar to components ofoptical engine 700 and components of laser writing system 800. Unlesscontext below dictates otherwise, the disclosure of components in FIG. 7and FIG. 8 is applicable to similarly numbered components in FIG. 10Aand will not be repeated in the interests of brevity. Photonicintegrated circuit writing system 1000 a includes laser writing system800, which, during operation, writes a photonic integrated circuit in ablock of writeable glass 820 in a manner similar to the operation oflaser writing system 800 described above with reference to FIG. 8.Photonic integrated circuit writing system 1000 a can be utilized tomanufacture an optical engine using a process that is similar in atleast some respects to method 900 of FIG. 9, but with photonicintegrated circuit writing system 1000 a, act 914 can be performedbefore act 912, as detailed below.

Writeable glass 820 is bonded to cap 720 prior to writing a photonicintegrated circuit therein, using any of the bonding techniquesdiscussed above. The writeable glass 820 may comprise a contiguous pieceof glass or similar transparent material that undergoes a change inrefractive index when exposed to high-intensity laser light. Bonding thewriteable glass to the cap includes positioning and orienting thewriteable glass 820 relative to each laser diode 710 to place thewriteable glass 820 in the path of the beam of light emitted by eachlaser diode 710, such that the beam of light emitted by each laser diode710 impinges on the writeable glass.

Writeable glass 820 can be positioned against optical window 730, suchthat beams of light from laser diodes 710 pass through optical window730 directly into writeable glass 820. Alternatively, the writeableglass 820 may optionally form optical window 730.

The entire base substrate 702 and all components bonded thereto can bephysically coupled to translatable mount 830, such as with clamps 821,adhesives, and/or any other appropriate coupling mechanism. Suchcoupling mechanism is preferably removable, such that base substrate 702and all components bonded thereto can be detached from translatablemount 830 after laser writing of writeable glass 820 is complete.

With writeable glass 820 bonded to base substrate 702 indirectly via cap720, and base substrate 702 physically coupled to translatable mount830, at least one waveguide 822 can be laser written into writeableglass 820 by translating base substrate 702 and all components thereonusing translatable mount 830. At least one input facet 612 (for exampleat least one grating input coupler) can also be written into writeableglass 820 by translating base substrate 702 and all components thereonusing translatable mount 830. Consequently, writeable glass 820 becomesa photonic integrated circuit.

To determine where the at least one waveguide 822 should be written,laser diodes 710 could be activated, thus causing beams of lighttherefrom to impinge on writeable glass 820. Writing laser 810 can bealigned to directly write waveguides and input facets (e.g. gratingcouplers as shown in FIG. 10A) at the exact location where the beams oflight from laser diodes 710 impinge on the writeable block 820. In thisway, the input facets of the resulting photonic integrated circuit willbe accurately aligned with the laser diodes, ensuring efficientincoupling of the beams of light into the photonic integrated circuit.

Alternatively, the writeable glass 820 could be illuminated, such as bybeing backlit if base substrate 702 is at least partially transparent.Writing laser 810 can then be aligned to directly write waveguides basedon locations of shadows caused by laser diodes 710, CoS's 712 andoptical redirector element 718. In this way, the input facets of theresulting photonic integrated circuit will be accurately aligned withthe laser diodes, ensuring efficient incoupling of the beams of lightinto the photonic integrated circuit.

Aligning the input facets of the photonic integrated circuit to thebeams of light during the writing stage will be more accurate thantrying to mechanically align a pre-fabricated photonic integratedcircuit, due to deviations that can arise in the bonding processes ofnot only the pre-fabricated photonic integrate circuit, but also thelaser diodes. As one example, if each of four laser diodes is randomlymisaligned, it would be difficult to align a prefabricated photonicintegrated circuit to match the beam of light from each diode, since notonly could the photonic integrated circuit be misaligned during thebonding processes, but also the spacing between each laser diode may notmatch the spacing between each waveguide in the photonic integratedcircuit due to the random misalignment of each of the laser diodes.Direct laser writing the photonic integrated circuit after all of thecomponents have been mechanically bonded obviates these issues, byallowing the position and spacing of each laser diode relative to thewriteable glass to be accounted for after bonding is complete.

FIG. 10B is a left side sectional view of photonic integrated circuitwriting system 1000 b. Photonic integrated circuit writing system 1000 bincludes components that may be substantively similar to components ofphotonic integrated circuit writing system 1000 a as discussed withregards to FIG. 10A. Unless context below dictates otherwise, thedisclosure related to components in FIG. 10A is applicable to similarlynumbered components in FIG. 10B and will not be repeated in theinterests of brevity.

In FIG. 10B, instead of writing the input facets of the photonicintegrated circuit 600 as grating input couplers, a reflective surfaceis instead written to redirect input beams of light 610 into at leastone waveguide 822 of photonic integrated circuit 600. For example, theat least one reflective surface could be a planar region with lowerindex of refraction than the material from which writeable glass 820 isformed. Consequently, laser light 610 can be redirected by the planarregion with lower index of refraction due to total internal reflection.

Additionally, FIG. 10B illustrates an implementation in which at leastone laser diode 710 is a vertical-cavity surface-emitting laser (VCSEL),such that laser light emitted by the laser diode is directed towardsoptical window 730 without the need for an optical redirecting element.Such a laser diode setup could be implemented in any of theimplementations discussed herein. The implementation of FIG. 10B doesnot require the use of a VCSEL, but could instead use a side emittinglaser with an optical redirecting element such as shown in FIGS. 1A and1B.

In some implementations, a photonic integrated circuit could bemanufactured using a combination of the techniques described withreference to FIGS. 8, 9, 10A, and 10B, as discussed below.

In one example, a large portion of a photonic integrated circuit couldbe first written, except for a small portion of the photonic integratedcircuit at the input of writeable glass. Subsequently, the photonicintegrated circuit could be bonded to the cap such as in FIG. 10, andthe remaining small portion of the photonic integrated circuit at theinput of the writeable glass could be written to couple the output ofeach laser diode to the portion of the photonic integrated circuit whichis already written.

In another example, a first photonic integrated circuit could be writtenas in FIG. 8. Subsequently, the first photonic integrated circuit couldbe bonded to the cap similar to as in FIG. 7, with the first photonicintegrated circuit being offset from the output of each laser diode suchthat the output from each laser diode does not impinge on the firstphotonic integrated circuit. In the area in the output path of eachlaser diode, a block of writeable glass could be bonded to the cap.Subsequently, a second photonic integrated circuit could be written inthe writeable glass similar to in FIGS. 10A and 10B to couple the outputof each laser diode to an input edge of the previously written firstphotonic integrated circuit. In this example, the block of writeableglass could be formed as the optical window, and/or could be formed tocover a portion of the first photonic integrate circuit.

FIGS. 11A and 11B are isometric views showing implementations of opticalengines having differing positions for a laser diode driver circuit. Theimplementations shown in FIGS. 11A and 11B are similar in at least somerespects to the implementation of FIGS. 1A and 1B, and one skilled inthe art will appreciate that the description regarding FIGS. 1A and 1Bis applicable to the implementations of FIGS. 11A and 11B unless contextclearly dictates otherwise.

FIG. 11A shows an optical engine 1100 a which includes a base substrate1102. The base substrate 1102 may be formed from a material that isradio frequency (RF) compatible and is suitable for hermetic sealing.For example, the base substrate 1102 may be formed from low temperatureco-fired ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar®, etc.

The optical engine 1100 a also includes a plurality of laser diodesaligned in a row across a width of the optical engine 1100 a, includingan infrared laser diode 1110 a, a red laser diode 1110 b, a green laserdiode 1110 c, and a blue laser diode 1110 d. In operation, the infraredlaser diode 1110 a provides infrared laser light, the red laser diode1110 b provides red laser light, the green laser diode 1110 c providesgreen laser light, and the blue laser diode 1110 d provides blue laserlight. Each of the laser diodes may comprise one of an edge emitterlaser or a vertical-cavity surface-emitting laser (VCSEL), for example.In FIG. 11A, laser diodes 1110 a, 1110 b, 1110 c, and 1110 d are shownas being bonded (e.g., attached) directly to base substrate 1102, asdescribed above with regards to act 504 in FIG. 5, but one skilled inthe art will appreciate that laser diodes 1110 a, 1110 b, 1110 c, and1110 d could each be mounted on a respective submount, similar to as inFIGS. 1A and 1B.

The optical engine 1100 a also includes a laser diode driver circuit1114 which can be bonded to the same surface of base substrate 1102 asthe laser diodes 1110 a, 1110 b, 1110 c, 1110 d. In alternativeimplementations, laser diode driver circuit 1114 can be bonded to aseparate base substrate, such as in FIG. 11B discussed later. The laserdiode driver circuit 1114 is operatively coupled to the plurality oflaser diodes 1110 a, 1110 b, 1110 c, and 1110 d via respectiveelectrical connections 1116 a, 1116 b, 1116 c, 1116 d to selectivelydrive current to the plurality of laser diodes. In at least someimplementations, the laser diode driver circuit 1114 may be positionedrelative to the laser diodes 1110 a, 1110 b, 1110 c, and 1110 d tominimize the distance between the laser diode driver circuit 1114 andthe laser diodes. Although not shown in FIG. 11A, the laser diode drivercircuit 1114 may be operatively coupleable to a controller (e.g.,microcontroller, microprocessor, ASIC) which controls the operation ofthe laser diode driver circuit 1114 to selectively modulate laser lightemitted by the laser diodes 1110 a, 1110 b, 1110 c, and 1110 d. In atleast some implementations, the laser diode driver circuit 1114 may bebonded to another portion of the base substrate 1102, such as the bottomsurface of the base substrate 1102. In at least some implementations,the laser diode driver circuitry 1114 may be remotely located andoperatively coupled to the laser diodes 1110 a, 1110 b, 1110 c, and 1110d. In order to not require the use of impedance matched transmissionlines, the size scale may be small compared to a wavelength (e.g.,lumped element regime), where the electrical characteristics aredescribed by (lumped) elements like resistance, inductance, andcapacitance.

Proximate the laser diodes 1110 a, 1110 b, 1110 c, and 1110 d there ispositioned an optical director element 1118. Like the laser diodes 1110a, 1110 b, 1110 c, and 1110 d, the optical director element 1118 isbonded to the top surface of the base substrate 1102. The opticaldirector element 1118 may be bonded proximate to or adjacent each of thelaser diodes 1110 a, 1110 b, 1110 c, and 1110 d. In the illustratedexample, the optical director element 1118 has a triangular prism shapethat includes a plurality of planar faces, similar to optical directorelement 118 in FIGS. 1A and 1B. The optical director element 1118 maycomprise a mirror or a prism, for example.

The optical engine 1100 a also includes a cap 1120 similar to cap 120 inFIGS. 1A and 1B. For clarity, cap 1120 is shown as being transparent inFIG. 11A, though this is not necessarily the case, and cap 1120 can beat least partially formed of an opaque material. Cap 1120 includes ahorizontal optical window 1130 that forms the “top” of the cap 1120.Although optical window 1130 in FIG. 11A is shown as comprising theentire top of cap 1120, in alternative implementations optical windowcould comprise only a portion of the top of cap 1120. Cap 1120 includingoptical window 1130 defines an interior volume sized and dimensioned toreceive the plurality of laser diodes 1110 a, 1110 b, 1110 c, 1110 d,and the optical director element 1118. Cap 1120 is bonded to the basesubstrate 1102 to provide a hermetic or partially hermetic seal betweenthe interior volume of the cap 1120 and a volume exterior to the cap1120.

The optical director element 1118 is positioned and oriented to direct(e.g., reflect) laser light received from each of the plurality of laserdiodes 1110 a, 1110 b, 1110 c, and 1110 d upward toward the opticalwindow 1130 of the cap 1120, wherein the laser light exits the interiorvolume, similar to FIGS. 1A and 1B.

The cap 1120 may have a round shape, rectangular shape, or other shape,similarly to as described regarding FIGS. 1A and 1B above. The opticalwindow 1130 may comprise an entire top of the cap 1120, or may compriseonly a portion thereof. In at least some implementations, the opticalwindow 1130 may be located on a sidewall of cap 1120 rather thanpositioned as a top of the cap 1120, and the laser diodes 1110 a, 1110b, 1110 c, 1110 d and/or the optical director element 1118 may bepositioned and oriented to direct the laser light from the laser diodestoward the optical window on the sidewall. In at least someimplementations, the laser diodes 1110 a, 1110 b, 1110 c, and 1110 d maybe positioned and oriented to direct the laser light from the laserdiode toward the optical window on the sidewall without optical directorelement 1118. In at least some implementations, the cap 1120 may includea plurality of optical windows instead of a single optical window.

The optical engine 1100 a can also include four collimation/pointinglenses similarly to as discussed regarding FIGS. 1A and 1B above andFIGS. 12A and 12B below. Each of the collimation lenses can be operativeto receive laser light from a respective one of the laser diodes 1110 a,1110 b, 1110 c, or 1110 d, and to generate a single color beam.

The optical engine 1100 a may also include, or may be positionedproximate to, a beam combiner that is positioned and oriented to combinethe light beams received from each of the collimation lenses or laserdiodes 1110 a, 1110 b, 1110 c, or 1110 d into a single aggregate beam.As an example, the beam combiner may include one or more diffractiveoptical elements (DOE) and/or one or more refractive/reflective opticalelements that combine the different color beams in order to achievecoaxial superposition. Exemplary beam combiners are shown and discussedwith reference to FIGS. 3, 12A, 12B, and 12C.

In at least some implementations, the laser diodes 1110 a, 1110 b, 1110c, 1110 d, the optical director element 1118, and/or the collimationlenses may be positioned differently. As noted above, laser diode drivercircuit 1114 may be mounted on a top surface or a bottom surface of thebase substrate 1102, depending on the RF design and other constraints(e.g., package size). In at least some implementations, the opticalengine 1100 a may not include the optical director element 1118, and thelaser light may be directed from the laser diodes 1110 a, 1110 b, 1110c, and 1110 d toward collimation lenses without requiring anintermediate optical director element, such as illustrated in FIGS. 12Aand 12B. Additionally, in at least some implementations, one or more ofthe laser diodes may be mounted indirectly on the base substrate 1102with a submount.

Optical engine 1100 a in FIG. 11A also includes an electricallyinsulating cover 1140. In FIG. 11A, laser diodes 1110 a, 1110 b, 1110 c,and 1110 d are each connected to laser diode driver circuitry 1114 by arespective electrical connection 1116 a, 1116 b, 1116 c, or 1116 dpositioned as described above with regards to act 508 in FIG. 5.Electrical connections 1116 a, 1116 b, 1116 c, and 1116 d run across asurface of the base substrate 1102. As described above with regards toact 510 in FIG. 5, electrically insulating cover 1140 is placed,adhered, formed, or otherwise positioned over electrical connections1116 a, 1116 b, 1116 c, and 1116 d, such that each of the electricalconnections 1116 a, 1116 b, 1116 c, and 1116 d run through electricallyinsulating cover 1140. Also as described above with regards to act 510in FIG. 5, cap 1120 is placed, adhered, formed, or otherwise positionedover electrically insulating cover 1140, such that cap 1120 does notcontact any of the electrical connections 1116 a, 1116 b, 1116 c, or1116 d. For clarity, cap 1120 is shown as being transparent in FIG. 11A,though this is not necessarily the case, and cap 1120 can be at leastpartially formed of an opaque material. Electrically insulating cover1140 can be formed of a material with low electrical permittivity suchas a ceramic, such that electrical signals which run through electricalconnections 1116 a, 1116 b, 1116 c, and 1116 d do not run into orthrough electrically insulating cover 1140. In this way, electricalsignals which run through electrical connections 1116 a, 1116 b, 1116 c,and 1116 d can be prevented from running into or through cap 1120, whichcan be formed of an electrically conductive material. Although FIG. 11Ashows electrically insulating cover 1140 as extending along only part ofa side of cap 1120, one skilled in the art will appreciate thatelectrically insulating cover 1140 can extend along an entire sidelength of cap 1120.

One skilled in the art will appreciate that the positions of laser diodedriver circuitry 1114, electrical connections 1116 a, 1116 b, 1116 c,1116 d, and electrically insulating cover 1140 as shown in FIG. 11Acould also be applied in other implementations of the subject systems,devices and methods. For example, in the implementations of FIGS. 1A and1B, laser diode driver circuitry 114 could be positioned on top surface104 of base substrate 102, and electrical connections 116 could runacross top surface 104 under an electrically insulating cover, such thatelectrical connections 116 do not contact any conductive portion of cap120.

FIG. 11B is an isometric view an optical engine 1100 b similar in atleast some respects to optical engine 1100 a of FIG. 11A. One skilled inthe art will appreciate that the description of optical engine 1100 a inFIG. 11A is applicable to optical engine 1100 b in FIG. 11B, unlesscontext clearly dictates otherwise. The optical engine 1100 b includes abase substrate 1103 a. Similar to base substrate 1102 in FIG. 11A, basesubstrate 1103 a may be formed from a material that is radio frequency(RF) compatible and is suitable for hermetic sealing. For example, thebase substrate 1103 a may be formed from low temperature co-firedceramic (LTCC), alumina, Kovar®, etc.

One difference between optical engine 1100 b in FIG. 11B and opticalengine 1100 a in FIG. 11A relates to what components are bonded (e.g.attached) to base substrate 1103 a. In optical engine 1100 b, each of:laser diodes 1110 a, 1110 b, 1110 c, 1110 d; cap 1120; electricalconnections 1116 a, 1116 b, 1116 c, 1116 d; and electrically insulatingcover 1140 are bonded (e.g., attached) to base substrate 1103 a.However, laser diode driver circuit 1114 is not necessarily bondeddirectly to base substrate 1103 a. Instead, laser diode driver circuit1114 could be bonded to a separate base substrate 1103 b. Similar tobase substrate 1102 in FIG. 11A and base substrate 1103 a in FIG. 11B,base substrate 1103 b may be formed from a material that is radiofrequency (RF) compatible and is suitable for hermetic sealing. Forexample, the base substrate 1103 b may be formed from low temperatureco-fired ceramic (LTCC), alumina, Kovar®, etc. In an alternativeimplementation, laser diode drive circuit 1114 may not need to be bondedto a substrate at all, and could simply be mounted directly within aframe of a WHUD.

For implementations where laser diode drive circuit 1114 is not bondedto base substrate 1103 a, electrical contacts 1117 a, 1117 b, 1117 c,and 1117 d could be bonded to base substrate 1103 a, each at an end of arespective electrical connection 1116 a, 1116 b, 1116 c, or 1116 d asdescribed above with regards to act 508 in FIG. 5. In this way,electrical contacts 1117 a, 1117 b, 1117 c, and 1117 d could be used toelectrically couple laser diode drive circuit 1114 to electricalconnections 1116 a, 1116 b, 1116 c, and 1116 d and consequently laserdiodes 1110 a, 1110 b, 1110 c, and 1110 d.

In some implementations, an optical engine similar to optical engine 700may include a beam combiner 316 as described with regards to FIG. 3 inplace of photonic integrated circuit 600. FIG. 12A illustrates anexemplary optical engine 1200 a in this regard.

FIG. 12A is a side sectional view of optical engine 1200 a. The opticalengine 1200 includes several components that may be similar or identicalto the components of the optical engine 100 of FIGS. 1A and 1B and/orthe optical engine 700 of FIG. 7. Thus, some or all of the discussionabove may be applicable to the optical engine 1200 a.

The optical engine 1200 a includes a base substrate 1202. The basesubstrate 1202 may be formed from a material that is radio frequency(RF) compatible and is suitable for hermetic sealing. For example, thebase substrate 1202 may be formed from low temperature co-fired ceramic(LTCC), aluminum nitride (AlN), alumina, Kovar®, etc.

The optical engine 1200 a also includes a plurality of laser diodes 1210a, 1210 b, 1210 c, 1210 d bonded thereto. The plurality of laser diodescould include an infrared laser diode 1210 d which provides infraredlaser light 1238 d, a red laser diode 1210 a which provides red laserlight 1238 a, a green laser diode 1210 b which provides green laserlight 1238 b, and a blue laser diode 1210 c which provides blue laserlight 1238 c. Each of the laser diodes 1210 a, 1210 b, 1210 c, and 1210d may comprise one of an edge emitter laser or a vertical-cavitysurface-emitting laser (VCSEL), for example. For ease of illustration,each of the laser diodes in FIG. 12A is shown as a VCSEL, but it iswithin the scope of the present systems, devices, and methods to use anedge emitting laser and an optical redirector element such as shown inFIGS. 1A and 1B instead. For clarity, each of the laser diodes is shownas being bonded directly to base substrate 1202, but in someimplementations each laser diode could be bonded to a respectivesubmount that is bonded to the base substrate 1202. The plurality oflaser diodes 1210 a, 1210 b, 1210 c, and 1210 d are aligned in a rowacross a width of the optical engine 1200 a between the left and rightsides thereof.

Although not explicitly shown in FIG. 12A, the optical engine 1200 a caninclude a laser diode driver circuit which selectively drives each ofthe laser diodes. Such a laser diode driver circuit can be bonded to atop surface of base substrate 1202 similar to as in FIG. 11A, bonded toanother portion of the base substrate 1202 such as a bottom surface ofthe base substrate 1202 similar to in FIGS. 1A, 1B and 7, or separatefrom the base substrate 1202 similar to in FIG. 11B. Such a laser diodedriver circuit may be operatively coupleable to a controller (e.g.,microcontroller, microprocessor, ASIC) that controls the operation ofthe laser diode driver circuit to selectively modulate laser lightemitted by the laser diodes 1210 a, 1210 b, 1210 c, and 1210 d. In atleast some implementations, the laser diode driver circuitry may beremotely located and operatively coupled to the laser diodes 1210 a,1210 b, 1210 c, and 1210 d. In order to not require the use of impedancematched transmission lines, the size scale may be small compared to awavelength (e.g., lumped element regime), where the electricalcharacteristics are described by (lumped) elements like resistance,inductance, and capacitance.

The optical engine 1200 a also includes a cap 1220, which can be similarto cap 720 as discussed regarding FIG. 7. Within a portion of the cap1220 there is an optical window 1230 positioned proximate the laserdiodes 1210 a, 1210 b, 1210 c, and 1210 d to pass light therefrom out ofthe cap 1220. The cap 1220 and optical window 1230 define an interiorvolume 1232 sized and dimensioned to receive the plurality of laserdiodes 1210 a, 1210 b, 1210 c, and 1210 d. Cap 1220 is bonded to thebase substrate 1202 to provide a hermetic seal or a partial hermeticseal between the interior volume 1232 of the cap and a volume exteriorto the cap.

The cap 1220 may have a round shape, rectangular shape, or other shape.The optical window 1230 may comprise an entire side of the cap 1220, ormay comprise only a portion thereof. In at least some implementations,the cap 1220 may include a plurality of optical windows instead of asingle optical window 1230.

The optical engine 1200 a can include four collimation/pointing lenses1236 a, 1236 b, 1236 c, and 1236 d, one for each respective laser diode1210 a, 1210 b, 1210 c, and 1210 d. Each of the plurality of collimationlenses 1236 a, 1236 b, 1236 c, and 1236 d can be positioned and orientedto receive light from a corresponding one of the laser diodes 1210 a,1210 b, 1210 c, and 1210 d through the optical window 1230. In someimplementations, each of the collimation lenses can be bonded to opticalwindow 1230. In other implementations, the optical window 1230 can beformed to include each of the collimation lenses.

The collimation lenses 1236 a, 1236 b, 1236 c, and 1236 d couple therespective beams of light 1238 a, 1238 b, 1238 c, and 1238 d intorespective optical elements 328, 330, 332, and 334 of a beam combiner316. Beam combiner 316 in FIG. 12A could be similar to beam combiner 316illustrated in FIG. 3, such that the description regarding FIG. 3 can beapplicable to the beam combiner 316 in FIG. 12A. The beam combiner 316may be bonded to the collimation lenses 1236 a, 1236 b, 1236 c, and 1236d. As discussed above regarding FIG. 3, in operation, beam combiner 316receives a plurality of beams of light 1238 a, 1238 b, 1238 c, and 1238d and combines the plurality of beams to provide a coaxiallysuperimposed aggregate beam of light 336.

In at least some implementations, at least some of the components may bepositioned differently. As noted above, the laser diode driver circuit1214 may be mounted on a top surface or a bottom surface of the basesubstrate 1202, or may be positioned remotely therefrom, depending onthe RF design and other constraints (e.g., package size). In at leastsome implementations, the optical engine 1200 a may include an opticaldirector element (e.g., optical director element 118 of FIG. 1), and thelaser light may be directed from the laser diodes 1210 a, 1210 b, 1210c, and 1210 d toward the collimation lenses 1236 a, 1236 b, 1236 c, 1236d via an intermediate optical director element.

Even though FIG. 12A shows a gap between the collimation lenses and theoptical window 1230, it is within the scope of the present systems,devices, and methods to bond the collimation lenses directly to theoptical window 1230, or to form the collimation lenses as part of theoptical window 1230. Further, even though FIG. 12A shows a gap betweenthe collimation lenses and the beam combiner 316, it is within the scopeof the present systems, devices, and methods to bond the collimationlenses directly to beam combiner 316, or to form beam combiner 316 andthe collimation lenses together as a single element.

For the sake of a controlled atmosphere inside the interior volume 1232,it may be desirable to have no organic compounds inside the interiorvolume 1232. In at least some implementations, the components of theoptical engine 1200 a may be bonded together using no adhesives. Inother implementations, a low amount of adhesives may be used to bond atleast one of the components, which may reduce cost while providing arelatively low risk of organic contamination for a determined lifetime(e.g., 2 or more years) of the optical engine 1200 a. Similarly to asdetailed above regarding FIGS. 1A and 1B, partial hermeticity, aparticulate dust cover, or even no protective cover may be acceptablefor certain applications. Various bonding processes (e.g., attachingprocesses) for the optical engine 1200 a are discussed above withreference to FIG. 5.

Due to the divergent beam from each of the laser diodes 1210 a, 1210 b,1210 c, and 1210 d and the lateral distances between the laser diodes,the collimation lenses 1236 a, 1236 b, 1236 c, and 1236 d, and the beamcombiner 316, it may be advantageous to minimize a distance between therespective output facets of the laser diodes 1210 a, 1210 b, 1210 c, and1210 d and the optical window 1230. For the same reason, it may beadvantageous to minimize the thickness of the optical window 1230 sothat the collimation lenses 1236 a, 1236 b, 1236 c, and 1236 d can bepositioned relatively close to the output facets of the laser diodes1210 a, 1210 b, 1210 c, and 1210 d.

In at least some implementations, the collimation lenses 1236 a, 1236 b,1236 c, and 1236 d may be actively aligned. In at least someimplementations, the laser diodes 1210 a, 1210 b, 1210 c, and 1201 d,the cap 1220 (including optical window 1230), and/or the beam combiner316 may be passively aligned.

FIGS. 12B and 12C illustrate alternative implementations of the opticalengine 1200 a shown in FIG. 12A. One skilled in the art will appreciatethat, unless context clearly dictates otherwise, the description of FIG.12A is applicable to the implementations of FIGS. 12B and 12C.

FIG. 12B is a side sectional view of an optical engine 1200 b similar tooptical engine 1200 a of FIG. 12A. Optical engine 1200 b includes a beamcombiner 317 which is similar to beam combiner 316 as shown in FIG. 12A,but bigger in size relative to the other components of FIG. 12B. Beamcombiner 317 functions to produce an aggregate beam 337 in a similarmanner to how beam combiner 316 produces aggregate beam 336 as disclosedregarding FIGS. 3A and 3B, such that the descriptions throughout thisapplication pertaining to beam combiner 316 are applicable to beamcombiner 317. Further, the descriptions pertaining to optical elements328, 330, 332, and 334 of beam combiner 316 are applicable to opticalelements 329, 331, 333, and 335 of beam combiner 317.

In optical engine 1200 b of FIG. 12B, beam combiner 317 is large in sizerelative to the other components of the FIG. 12B, such that each lightbeam 1238 a, 1238 b, 1238 c, and 1238 d does not line up directly with arespective optical element 329, 331, 333, and 335. To address thisissue, at least one of collimation lens 1236 a, 1236 b, 1236 c, and 1236d can be aligned to redirect a respective light beam 1238 a, 1238 b,1238 c, or 1238 d towards a respective optical element 329, 331, 333, or335. As an example, at least one collimation lens 1236 a, 1236 b, 1236c, or 1236 d could be rotated with respect to a respective beam of light1238 a, 1238 b, 1238 c, or 1238 d. As another example, at least onecollimation lens 1236 a, 1236 b, 1236 c, and 1236 d could be formed in askewed shape which redirects a respective beam of light 1238 a, 1238 b,1238 c, or 1238 d appropriately. As another example, at least onecollimation lens 1236 a, 1236 b, 1236 c, or 1236 d could include awaveguide, or be formed as a waveguide, to redirect a respective beam oflight 1238 a, 1238 b, 1238 c, or 1238 d. Even though FIG. 12B shows agap between the collimation lenses and the optical window 1230, it iswithin the scope of the present systems, devices, and methods to bondthe collimation lenses directly to the optical window 1230, or to formthe collimation lenses as part of the optical window 1230. Further, eventhough FIG. 12B shows a gap between the collimation lenses and the beamcombiner 317, it is within the scope of the present systems, devices,and methods to bond the collimation lenses directly to beam combiner317, or to form beam combiner 317 and the collimation lenses together asa single element.

FIG. 12C is a side sectional view of an optical engine 1200 c similar tooptical engine 1200 a of FIG. 12A and optical engine 1200 b of FIG. 12B.Optical engine 1200 c includes a collimation lens 1237 positioned nearan output side of beam combiner 316. In one implementation, collimationlens 1237 could replace collimation lenses 1236 a, 1236 b, 1236 c, and1236 d, such that uncollimated beams of light 1238 a, 1238 b, 1238 c,and 1238 d enter beam combiner 316, and collimation lens 1237 collimatesaggregate beam 336 output from beam combiner 316. In anotherimplementation, collimation lens 1237 could be in addition tocollimation lenses 1236 a, 1236 b, 1236 c, and 1236 d, such that roughlycollimated or partially collimated beams of light 1238 a, 1238 b, 1238c, and 1238 d enter beam combiner 316, and collimation lens 1237 fullycollimates and/or corrects aggregate beam 336 output from beam combiner316.

Throughout this application, collimation lenses have been represented inthe Figures by a simple curved lens shape. However, the subject systems,devices, and methods can utilize more advanced collimation schemes, asappropriate for a given application.

FIG. 13 shows an exemplary situation where using an advanced collimationscheme would be helpful. FIG. 13 is an isometric view of a laser diode1300. The laser diode 1300 may be similar or identical to the variouslaser diodes discussed herein. The laser diode 1300 outputs a laserlight beam 1302 via an output facet 1304 of the laser diode. FIG. 13shows the divergence of the light 1302 emitting from the laser diode1300. As shown, the light beam 1302 may diverge by a substantial amountalong a fast axis 1306 (or perpendicular axis) and by a lesser amount inthe slow axis 1308 (parallel axis). As a non-limiting example, in atleast some implementations, the light beam 1302 may diverge with fullwidth half maximum (FWHM) angles of up to 40 degrees in the fast axisdirection 1306 and up to 10 degrees in the slow axis direction 1308.This divergence results in a rapidly expanding elliptical cone.

FIGS. 14A and 14B show an exemplary collimation scheme that can be usedto circularize and collimate an elliptical beam such as that shown inFIG. 13. FIG. 14A illustrates an orthogonal view of the fast axis 1306of light beam 1302 emitted from laser diode 1300. FIG. 14B illustratesan orthogonal view of the slow axis 1308 of light beam 1302 emitted fromlaser diode 1300. As shown in FIG. 14A, a first lens 1400 collimateslight beam 1302 along fast axis 1306. As shown in FIG. 14B, first lens1400 is shaped so as to not substantially influence light beam 1302along slow axis 1308. Subsequently, as shown in FIG. 14B, light beam1302 is collimated along slow axis 1308 by a second lens 1402. As shownin FIG. 14A, second lens 1402 is shaped so as to not substantiallyinfluence light beam 1302 along fast axis 1306. In essence, light beam1302 is collimated along fast axis 1306 separately from slow axis 1308.By collimating light beam 1302 along fast axis 1306 separately from slowaxis 1308, the collimation power applied to each axis can beindependently controlled by controlling the power of lens 1400 and lens1402 separately. Further, spacing between each of laser diode 1300, lens1400, and lens 1402 can be controlled to collimate light beam 1302 to acertain width in each axis separately. If light beam 1302 is collimatedalong fast axis 1306 to the same width as slow axis 1308, light beam1302 can be circularized. Because light beam 1302 will typically divergefaster in the fast axis 1306, it is generally preferable to collimatelight beam 1302 along fast axis 1306 first, then collimate light beam1302 along slow axis 1308 after. However, it is possible in certainapplications to collimate light beam 1302 along slow axis 1308 first,and subsequently collimate light beam 1302 along fast axis 1306 after.This can be achieved by reversing the order of first lens 1400 withsecond lens 1402, with respect to the path of travel of light beam 1302.

FIGS. 14C and 14D are isometric views which illustrate exemplary shapesfor lenses 1400 and 1402. Each of lens 1400 and 1402 can be for examplea half-cylinder as in FIG. 14C, a full cylinder as in FIG. 14D, aquarter cylinder, a three-quarter cylinder, any other partial cylinder,or any other appropriate shape. Lenses 1400 and 1402 can be similarlyshaped, or can have different shapes.

FIGS. 15A and 15B illustrate an alternative collimation scheme. FIG. 15Aillustrates an orthogonal view of the fast axis 1306 of light beam 1302emitted from laser diode 1300. FIG. 15B illustrates an orthogonal viewof the slow axis 1308 of light beam 1302 emitted from laser diode 1300.As shown in FIG. 15A, a first lens 1500 redirects light beam 1302 alongfast axis 1306, to reduce divergence of light beam 1302 along fast axis1306. As shown in FIG. 15B, first lens 1500 is shaped so as to notsubstantially influence light beam 1302 along slow axis 1308.Preferably, first lens 1500 will reduce divergence of light beam 1302along fast axis 1306 to match divergence of light beam 1302 along slowaxis 1308. That is, first lens 1500 preferably circularizes light beam1302. Subsequently, as shown in FIGS. 15A and 15B, light beam 1302 iscollimated along both fast axis 1306 and slow axis 1308 by a second lens1502. As shown in FIGS. 15A and 15B, second lens 1502 is shapedsimilarly with respect to both the fast axis 1306 and the slow axis1308, to evenly collimate light beam 1302. In essence, first lens 1500circularizes light beam 1302, and subsequently second lens 1502collimates light beam 1302 along both axes. First lens 1500 can forexample be shaped similarly to lens 1400 or lens 1402 discussed above,and shown in FIGS. 14C and 14D. Second lens 1502 can for example beshaped as a double convex lens as illustrated in FIG. 15C, or a singleconvex lens (convex on either side) as illustrated in FIG. 15D, or anyother appropriate shape of collimating lens.

The collimation schemes illustrated in FIGS. 14A-14D and 15A-15D, anddiscussed above could be used in place of any of the collimation lensesdescribed herein, including at least collimation lenses 136 a, 136 b,136 c, 136 d.

A person of skill in the art will appreciate that the teachings of thepresent systems, methods, and devices may be modified and/or applied inadditional applications beyond the specific WHUD implementationsdescribed herein. In some implementations, one or more optical fiber(s)may be used to guide light signals along some of the paths illustratedherein.

The WHUDs described herein may include one or more sensor(s) (e.g.,microphone, camera, thermometer, compass, altimeter, and/or others) forcollecting data from the user's environment. For example, one or morecamera(s) may be used to provide feedback to the processor of the WHUDand influence where on the display(s) any given image should bedisplayed.

The WHUDs described herein may include one or more on-board powersources (e.g., one or more battery(ies)), a wireless transceiver forsending/receiving wireless communications, and/or a tethered connectorport for coupling to a computer and/or charging the one or more on-boardpower source(s).

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious embodiments can be applied to other portable and/or wearableelectronic devices, not necessarily the exemplary wearable electronicdevices generally described above.

For instance, the foregoing detailed description has set forth variousembodiments of the devices and/or processes via the use of blockdiagrams, schematics, and examples. Insofar as such block diagrams,schematics, and examples contain one or more functions and/oroperations, it will be understood by those skilled in the art that eachfunction and/or operation within such block diagrams, flowcharts, orexamples can be implemented, individually and/or collectively, by a widerange of hardware, software, firmware, or virtually any combinationthereof. In one embodiment, the present subject matter may beimplemented via Application Specific Integrated Circuits (ASICs).However, those skilled in the art will recognize that the embodimentsdisclosed herein, in whole or in part, can be equivalently implementedin standard integrated circuits, as one or more computer programsexecuted by one or more computers (e.g., as one or more programs runningon one or more computer systems), as one or more programs executed by onone or more controllers (e.g., microcontrollers) as one or more programsexecuted by one or more processors (e.g., microprocessors, centralprocessing units, graphical processing units), as firmware, or asvirtually any combination thereof, and that designing the circuitryand/or writing the code for the software and or firmware would be wellwithin the skill of one of ordinary skill in the art in light of theteachings of this disclosure.

When logic is implemented as software and stored in memory, logic orinformation can be stored on any processor-readable medium for use by orin connection with any processor-related system or method. In thecontext of this disclosure, a memory is a processor-readable medium thatis an electronic, magnetic, optical, or other physical device or meansthat contains or stores a computer and/or processor program. Logicand/or the information can be embodied in any processor-readable mediumfor use by or in connection with an instruction execution system,apparatus, or device, such as a computer-based system,processor-containing system, or other system that can fetch theinstructions from the instruction execution system, apparatus, or deviceand execute the instructions associated with logic and/or information.

In the context of this specification, a “non-transitoryprocessor-readable medium” can be any element that can store the programassociated with logic and/or information for use by or in connectionwith the instruction execution system, apparatus, and/or device. Theprocessor-readable medium can be, for example, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus or device. More specific examples (anon-exhaustive list) of the computer readable medium would include thefollowing: a portable computer diskette (magnetic, compact flash card,secure digital, or the like), a random access memory (RAM), a read-onlymemory (ROM), an erasable programmable read-only memory (EPROM, EEPROM,or Flash memory), a portable compact disc read-only memory (CDROM),digital tape, and other non-transitory media.

The various embodiments described above can be combined to providefurther embodiments. To the extent that they are not inconsistent withthe specific teachings and definitions herein, at least the followingare incorporated herein by reference in their entirety: U.S. ProvisionalPatent Application Ser. No. 62/438,725, U.S. Non-Provisional patentapplication Ser. No. 15/848,265 (U.S. Publication Number 2018/0180885),U.S. Non-Provisional patent application Ser. No. 15/848,388 (U.S.Publication Number 2018/0180886), U.S. Provisional Patent ApplicationSer. No. 62/450,218, U.S. Non-Provisional patent application Ser. No.15/852,188 (U.S. Publication Number 2018/0210215), U.S. Non-Provisionalpatent application Ser. No. 15/852,282, (U.S. Publication Number2018/0210213), U.S. Non-Provisional patent application Ser. No.15/852,205 (U.S. Publication Number 2018/0210216), U.S. ProvisionalPatent Application Ser. No. 62/575,677, U.S. Provisional PatentApplication Ser. No. 62/591,550, U.S. Provisional Patent ApplicationSer. No. 62/597,294, U.S. Provisional Patent Application Ser. No.62/608,749, U.S. Provisional Patent Application Ser. No. 62/609,870,U.S. Provisional Patent Application Ser. No. 62/591,030, U.S.Provisional Patent Application Ser. No. 62/620,600, U.S. ProvisionalPatent Application Ser. No. 62/576,962, U.S. Provisional PatentApplication Ser. No. 62/760,835, U.S. Non-Provisional patent applicationSer. No. 16/201,664, U.S. Non-Provisional patent application Ser. No.16/168,690, U.S. Non-Provisional patent application Ser. No. 16/171,206,U.S. Non-Provisional patent application Ser. No. 16/203,221, and/or PCTPatent Application PCT/CA2018051344. Aspects of the embodiments can bemodified, if necessary, to employ systems, circuits and concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. An optical engine, comprising: a base substrate; a plurality of laserdiodes, each of the plurality of laser diodes bonded directly orindirectly to the base substrate; a cap comprising at least one wallthat, with the base substrate, defines an interior volume sized anddimensioned to receive at least the plurality of laser diodes, the capbeing bonded to the base substrate to provide a hermetic or partiallyhermetic seal between the interior volume of the cap and a volumeexterior to the cap; and a photonic integrated circuit comprising aplurality of input facets and at least one output facet, in operation,the photonic integrated circuit receives a plurality of beams of lightat respective ones of the plurality of input facets and wavelengthmultiplexes the plurality of beams of light to provide an aggregatedbeam of light at the output facet.
 2. The optical engine of claim 1wherein each of the plurality of laser diodes is positioned immediatelyadjacent a respective one of the plurality of input facets of thephotonic integrated circuit.
 3. The optical engine of claim 1 whereineach of the plurality of input facets of the photonic integrated circuitis positioned inside the interior volume and the at least one outputfacet of the photonic integrated circuit is positioned outside of theinterior volume.
 4. The optical engine of claim 1 wherein the capcomprises at least one optical window positioned and oriented to allowbeams of light emitted from the plurality of laser diodes to exit theinterior volume.
 5. The optical engine of claim 4 wherein the photonicintegrated circuit is bonded to the optical window of the cap.
 6. Theoptical engine of claim 4 wherein the at least one wall of the capcomprises at least one continuous sidewall having a lower first end andan upper second end, the lower first end bonded to the base substrate,and the optical window is hermetically or partially hermetically sealedto the cap proximate the upper second end.
 7. The optical engine ofclaim 4, further comprising an optical director element disposed withinthe interior volume, the optical director element bonded to the basesubstrate proximate the plurality of laser diodes, and positioned andoriented to reflect laser light from the plurality of laser diodestoward the optical window of the cap.
 8. The optical engine of claim 1,further comprising: a plurality of collimation lenses, each of theplurality of collimation lenses positioned and oriented to collimatelight received from respective ones of beams of light emitted from theplurality of laser diodes, and to output the collimated light toward tothe plurality of input facets of the photonic integrated circuit.
 9. Theoptical engine of claim 1, further comprising: a collimation lenspositioned and oriented to receive and collimate the aggregate beam oflight from the output facet of the photonic integrated circuit.
 10. Theoptical engine of claim 1, further comprising at least one diffractiveoptical element positioned and oriented to receive the aggregate beam oflight, in operation, the at least one diffractive optical elementprovides wavelength dependent focus correction for the aggregate beam oflight.
 11. The optical engine of claim 1, further comprising: aplurality of chip submounts bonded to the base substrate, wherein eachof the laser diodes are bonded to a corresponding one of the pluralityof chip submounts.
 12. The optical engine of claim 1 wherein theplurality of laser diodes includes a red laser diode to provide a redlaser light, a green laser diode to provide a green laser light, a bluelaser diode to provide a blue laser light, and an infrared laser diodeto provide infrared laser light.
 13. The optical engine of claim 1,further comprising at least one laser diode driver circuit operativelycoupled to the plurality of laser diodes to selectively drive current tothe plurality of laser diodes.
 14. The optical engine of claim 13wherein the at least one laser diode driver circuit is bonded to a firstsurface of the base substrate, and the plurality of laser diodes and thecap are bonded to a second surface of the base substrate, the secondsurface of the base substrate opposite the first surface of the basesubstrate.
 15. The optical engine of claim 13 wherein the at least onelaser diode driver circuit, the plurality of laser diodes, and the capare bonded to a first surface of the base substrate.
 16. The laserprojector of claim 13 wherein the plurality of laser diodes and the capare bonded to the base substrate, and the at least one laser diodedriver circuit is bonded to another substrate separate from the basesubstrate.
 17. The optical engine of claim 1 wherein each of the laserdiodes comprises one of an edge emitter laser or a vertical-cavitysurface-emitting laser (VCSEL).
 18. The optical engine of claim 1wherein the photonic integrated circuit comprises a plurality ofwaveguides, each waveguide of the plurality of waveguides to receivelaser light from a respective laser diode of the plurality of laserdiodes.
 19. The optical engine of claim 18, wherein each waveguide ofthe plurality of waveguides is optimized to receive and output laserlight having a wavelength corresponding to the wavelength of laser lightreceived from the respective laser diode.
 20. The optical engine ofclaim 18 wherein the plurality of waveguides comprises a waveguidecombiner.
 21. The optical engine of claim 20 wherein the waveguidecombiner comprises at least one of: a directional coupler, Y-branch,whispering gallery mode, or multi-mode interface coupler.
 22. Theoptical engine of claim 18 wherein each waveguide of the plurality ofwaveguides includes an input facet to receive laser light from arespective laser diode of the plurality of laser diodes and an outputfacet to output the received laser light, a spacing between the outputcouplers of each waveguide being smaller than a spacing between theinput facets of each waveguide.
 23. The optical engine of claim 1wherein each input facet of the plurality of input facets is a gratinginput coupler.
 24. The optical engine of claim 1 wherein each inputfacet of the plurality of input facets is a planar region with an indexof refraction lower than an index of refraction of material from whichthe photonic integrated circuit is formed.